Keep a running list on your coffee table. Two columns. One for things that need to be done, another for things that need to be purchased now and down the line. Your to-do list is going to be the big one- you'll think of new things to check, fix, or replace every day. You'll have fun doing everything, though, and end up having a really nice RV. Have fun!
P.S. There are lots of forums out there, and they all have some kind of checklist. Print yourself out one of those for starters, and then it's good every time you take off.