Hey, how's the training going?
Lot's of good tips already given. I'd definitely favour bodyglide over vaseline. Vaseline only seems to last about an hour for me. I chafe at the thighs and bodyglide always prevents that. Some on the toes and the balls of your feet should prevent blistering, double layer socks work great for me too.
A 10km race 2 months before and a 1/2 marathon 4/5 weeks before the full marathon will definitely stand to you and give you good experience.
On the day run your own race, don't worry if you get caught up behind slower runners, after a few miles the race will open up so i would avoid weaving in and out of people and running up and down off curbs, you'll only pay for it later.
I never bother with power bars or energy gels. i prefer just a handful of jellies for later on. You'll hear lots of talk about hitting the wall. I think if you are prepared enough and go at a steady pace you won't have that problem. It's a great feeling if you have some energy in the tank to pick up the pace coming to the line rather than struggling/walking over it.