It's fun being a nearly full-timer. We did 4 months, going north from Phoenix, AZ to Glacier and then east to Wisconsin and Illinois and back a few years ago and loved it. Probably the best suggestion is to go a short distance, 50-100 miles, and spend a week or so there to see what you forgot or really need.
2nd, is the mail and bill problem. Make a list of all of the expected bills, or everything that you pay through the mail or email, and make sure that you can pay them electronically from your bank -- assuming that you have a laptop with wifi and are comfortable using it. If you are reading this, you proably are. There are a lot of free WIFI sites, and many not free sites. You might be better to use your own cellphone broadband connection -- it is probably safer and more reliable than unknown freebie wifi sites.
Be sure your tires and everything else is in good condition before you start.
Make a number of short weekend trips ahead of time and try to do things like getting into Walmart parking lots etc. Practice makes perfect.
Subscribe to RV magazine -- they have a lot of tips there.
there are some campground clubs such as Passport and CampingWorlds Campground USA and Good Sams club that show a lot of plaes where you can staymore cheaply.