OK if you can do 9 miles in 8 minute miles that isn’t bad at all - a minute a mile is a big difference though. You need to be able to maintain 8 minute miles for 26.2 miles and that is hard but if you are starting out from that base I would say possible.
If you can do 3:30 then that is a respectable time - it’s the sort of time I would be looking to do if you gave me a month to prepare and that is off the back of a recent half and plenty of other training. I would look to run 9 miles in sub 7 minute miles (never actually ran a 9 mile race!) so you are looking at knocking a minute or two a mile off your pace for your current run and then doing some endurance work on top.
I’ve never run a marathon but most people in my club reckon that they aim to be doing 30 miles a week in training for one - but their best times are 2 40 - 3 hours so a bit quicker than your target - so I would say you could maybe get away with 20-25 miles a week for most of your training increasing towards the end then tapering down.
THere are lots of training schedules on sites like runners world (UK version) etc but they tend to be ambitious - in other words if I did the training they say you should I would hope to get a faster time than they reckon if you see what I mean. Personally I would be doing more miles than I think you want to but lets assume you want to run it on 3 sessions a week - here is an example of what you might do:
Sunday - Long run - aim to go about 9/10 minute miling (ie slower than your marathon target pace) and start it at 10 miles. Add a mile every week or two so that eventually you are up to 20/22 miles 2 weeks before the race. So in other words this Sunday you run 10 miles - in one or two weeks that increases to 11 etc etc. Do not go faster than this pace even though you can - the aim is just to build your aerobic threshold not to shag you out for the rest of the week - which when you are up to 20 miles odd will happen if you push it. If the pace becomes too hard as the miles increase then slacken the pace - this should be as comfortable as a run of that distance can be. A couple of weeks before the race you might increase the pace to see what happens !
Monday - gym and or cross train (cycle/ swim anything that doesn’t stress your legs)
Tuesday - Easy run of about half your Sunday run - same pace - this is basically a recovery run - you should not be too tired.
Wed - Gym / cross train
THursday - ****lek run of about 8 miles. Run for about a mile (10 minutes) easy jog - then up the pace to about 6 minute miling for 4 minutes - then another 10 minute slow jog - then another 4 minutes of 6 minute miling - then 1 minute slow jog - then another 6 minute miling 4 minutes - then 10 minutes slow jog etc until you have done about 8 miles. This should leave you absolutely bolloxed. (Not sure if this is technically a ****lek run btw!)
Alternative to this would be to run 10 miles gradually upping your pace - so you go from 2 miles at 10 minute miling - 2 at 9, 2 at 8 2 at 7 and 2 at 6. Sprint finish. Warm down. Again this should leave you bolloxed.
Thurs - Rest
Friday - Gym /cross train
Sat - rest
Hope that isn’t too ambitious but a 3.30 marathon is ambitious and there is no other way to run that time other than putting the miles in - if 20 mile training runs phase you then you should not be considering racing 26.2 (and at your pace you are racing not jogging - there are plenty of regular runners could not do that).
In the above do not be tempted to go faster or further early on - you don’t have to - running slower has benefits in terms of preventing burn out and injury - avoid sprint finishes except in your Thursday run - they will add relatively little benefit in a marathon and take a lot or recovery. Always stretch afterwards - if you find your legs are suffering a cold bath for as long as you can cope with might help too.
Very long cycle rides will help build aerobic fitness but will not condition the legs so whilst they may supplement your training in no way can they replace the running. Weights are used by good runners to guard against injury and increase speed - and to stop muscle wastage from too many long runs - but you are not going to gain endurance from them - or not the sort of endurance you need.
Also when you are running over an hour hydration becomes important - you might want to sort out a circuit so you can stuff a bottle of water/sports drink in your front garden to grab half way.
Shoes - there is a debate about this. Some people claim that traditional running shoes encourage you to have an unnatural running style (heel striking) which then encourages pronation and lots of other things that mean you need more padding/stability in your shoes which causes more problems etc etc THese people say you run naturally on the outside of the forefoot and that racing flats (fast light shoes with little cushioning as worn by elite atletes to race in) are actually better if you run properly. Certainly in X country running I run this way because the shoes allow it and I don’t get injured - whereas on roads I run traditionally on a fat heel and do get injured - but I have yet to try changing so wouldn’t like to offer advice other than to say there are two schools of thought.
I am going to assume you go with the majority on this - if you want to check out the alternative look at something like Gordon Pirie’s book or Michael Yessis amongst others.
Yes if you want traditional advice go to a running shop (has to be a specialist running shop I am afraid) and take your old running shoes with you. They will have a look - maybe use a treadmill - and fit you with what you need - budget up to £70 - alternatively find a couple of pairs you like, say you’ll think about it and then buy them off the web (check out Bourne Sports for one) at about £20 cheaper 
Tell them you want a marathon shoe - if you over pronate (if you are relatively flat footed you probably do) I think Adidas Supernova are good - quite light for a shoe with sufficient padding and stability. They reckon that a shoe should last 500 miles plus - for a marathon probably best be sure so bargain on getting 2 pairs to take you up to and over the marathon - don’t buy both together in case they don’t suit you but be aware they change the ranges so if you like them it is worth getting another pair the same before you need them - no point in getting used to different shoes if you don’t have to.
Let us know how you are getting on Stubbs, like I say if you can do 3 30 then you really have achieved something - without knowing you (so dont take it personally) I think you are maybe being ambitious - but then 8 minute miling for 9 miles off no real training is good so you may have a talent for it. Dont worry too much about your legs - Paula Radcliffe does nearly 150 miles a week for a marathon, Ovett used to do 100 for 1500 metres, Coe did 50 miles a week plus a lot of weight training and other stuff, and there are plenty of older athletes still running - I run some X country and stuff and you do see people in their 70s - I am not saying you can’t wear your joints out running but a lot of it is down to how you run - it certainly isn’t automatic. You needn’t worry about it training for one marathon - take glucosamine as a precaution if you want though. In terms of injury just start out slowly and build up - slacken off if you do get injured and most people are OK - tarmac is a lot softer than concrete too !
