Check out the Howto section off the main Adventure Cycling magazine pagehttp://www.adventurecycling.org/features/howto.cfm
for some introductory information on what to take, training, etc. Then come back here with specific questions.
Your route question is an interesting one. I'd suggest you head north to Virginia to start on the TransAmerica trail, possibly connecting with the Western Express. AC has done a good job of laying out a route, and locating places to stay, services, and points of interest. Maps are well worth the price. It's a good way to take your first tour; later, if you wish, you can strike out on your own route.
Alternately, I'd suggest you cut northwest to pick up the TransAm somewhere in Virginia or Kentucky. You'll cross some of the highest mountains east of the Mississippi on this route, where roads over the ridges tend to be sparse, and therefore relatively highly trafficed. (Another good reason to take the TransAm, at the risk of seeming repetitive!)