Go for it! You can definitely do it. 3 months sounds about right.
I've followed Hal Higdon's plans for the 2 marathons I've run. His half marathon plan is 12 weeks. He has you run 4 times the first week: two 3m runs, one 2m run, and one 4m run. So you'd need to be at a point where 3 or 4 miles doesn't beat you up too much before you start the 12-week plan.
http://www.halhigdon.com/halfmarathon/novice.htm
I've never tried a run-walk plan, but I've heard good things. Definitely worth looking into.
Check out the "race finder" at
www.runnersworld.com. I ran the Lexington marathon this past spring. It was well organized and followed a nice course through the horse country on the north side of town. Parking was a bit of a mess, and the weather was pretty awful, but overall it was a great race. I've also run the Indy 500 Festival half. Its main feature is that it's huge--35,000 runners. And you get to do a lap around the speedway, which is kinda neat (and the source of minor neck pains from 2+ miles on a banked track).
Get a good pair of shoes, preferably from a running shop where they take the time to help you pick a good shoe for your foot shape and stride. Fleet Feet is a chain that has stores in Louisville and Cincinnati. Perhaps someone local to Lexington can recommend a good store there.
Finally, listen to your body. Aches and pains are inevitable as you increase the mileage. But you want to avoid injury. Increase mileage gradually. Try to stick to a plan, but if you need a week off here and there, take it.
Good luck!
