I have done 4--2 Disney, 1 Twin Cities and 1 Chicago. Nope, you're not crazy. I never thought I'd do one either, and you'll find once you do one, you'll start thinking how could improve on your next one.You have the right mind set--to complete it injury free.
My first one I did the Jeff Galloway guidelines(pretty much, remember nothing is set in stone)and took 6 months to train--it was too long, the mental aspect was that it became a chore to train. 4 months(which it sounds like you are doing)will be perfect. Take a look at his training guide, I think it's on the runner's world website. The main thing is to slowly increase your long runs. I think it went something like this for long runs--depending on your base(which I did on saturday so I could rest on sunday)--6,7,8,9,10,5,11,6,12,7,etc.,. Don't stress over doing long runs during the week, just nice easy ones, the most important is your weekend long one. You do not have to train 26 miles to race 26 miles. My longest run was 18 and I did just fine. You will be surprised at how the crowds that cheer you on keep you going. The one piece I would advise you to train with is a Camelbak(or some type of fluid carrying system that works for you)--they make a smaller one, I don't remember the name but it's a baby blue color. I would map out my route and then drink roughly every mile or so. Just remember some runs will go better than others--you'll be training in warmer weather but doing the race in cooler weather, so don't worry about the pace, walk/run if you want--that's actually what Jeff Galloway does with his training groups and I've heard it works. I did upper body(but not crazy heavy)workouts because it will keep your arms from tiring out during the training. Good luck with everything and let us know how you do!! We'll be cheering you on!
Mary