Half Marathon anyone?

I have signed up for a half marathon training program. It seems as though I can only push myself to excersize effectively if I pay someone to keep me accountable. I was going to do the 10K training program, but I was the only one interested, so they decided not to have a 10K training for just one person. So, of course, I have not ran more than 3 miles since my 5K in July. Signing up for a half marathon will only force me to run my ass off every other day (you don't want to over train, so on my other days I'll do strengh training in the form of the Instanity workouts). I'm still the same weight and size as when I was last running, which is good, but I'm still looking to losse 20 pounds, but that will come eventually. I can run 13 miles with some training right? of course I can, people have done tougher things right? I'm nervous, but what else do I have to push me physically? Running, that's what I have.