I am proud to say I completed 4 marathons and several half's. That was several years ago - before kids. I expected the weight to just melt away, but that wasn't my experience (sorry). I learned to ignore the scale because I was heavier than I would've liked, but in phenominal shape. Six pounds in 3 weeks is not anything to scoff at. The thing about training is that you have to keep eating and rebuilding your muscles or you wont make it through the next session. Every runner is different, so you'll have to figure out what works best for you. I ran by times during the week (longest 50 minutes, I think) and by distance on Saturday mornings. I'd just get up and run during the week before work, but on Saturdays I'd make sure I ate something in the morning, and drink some coffee. Caffeine actually helps you not feel pain.
Carbo-loading is a good idea - but never weigh yourself once you're doing it because as your body's storing glycogen for the run, it's also storing water in your muscles so you'll weigh heavy. There are some really good books that you can use for ideas. I really liked Nancy Clark's Sports nutrition guidebook.
Are you training with a club? If not, I would recommend it.
Good luck! There is NOTHING like that feeling when you cross that finish line!
Fitday start date: 6/21/2010
Start weight: 158#
Goal met Spring 2011