I've been running competitively for 28 years and have done 13 marathons. That said, I don't want to be the one to pee on your Wheaties, but I can't recommend going from 0 to 26 in 19 weeks. Maybe concentrate on a more modest goal like a 10K or half-marathon to build up some experience. But if you're up for it, the Hal Higdon plan John Brew mentioned is what most newbies adhere to. Go in and have someone analyze your form so you can be fitted with the proper training shoes. Remember to respect the marathon, otherwise it will eat you up.