First Long Trip -- What are the "must dos" and "must haves"?

One resource I use is the sign one the interstate that says "gas this exit". With a 33' TT and the Excursion we were about 52' long and could fit in most all stations on the interstate.

If it isn't a holiday you don't need reservations if you stop early.
We have been across the U.S. a few times and spend about 4 or 5 months an the road a year and have never made reservations. If you aren't going to a destination park during in the peak of the season you will be fine

Relax and have fun.