We've taken 2 cross country trips with our old popup, 5 weeks in 2007, the kids were 14 & 6 and then 7 weeks in 2009 when they were 16 & 8. Did all the bills, etc. online. My husband was a teacher so summers off and I work remotely, so I did that too when I had a wifi signal.
I'd second "Next Exit" book. We also had the good sam book and maps, no gps used. Don't drive too far each day, we would stop by late afternoon, set up the trailer, take a quick dip in the campground pool, then dinner and rest. Each day I drove first, then my husband drove later and I would figure of where we might stay and call ahead. Didn't make any reservations, except for possibly a weekend where it might be harder to get a site. Also found quite a few free or really cheap places, like city parks, etc. that let you camp.
Definitely check the prescriptions, and all the standard tow vehicle/trailer related things like the oil, fluids, etc. Had everybody pack enough clothes for 8 days, then did laundry once a week. We hit all the national parks, visited friends in CA.
We have a truck with a cap, so we organized a lot of things into the back of it that we could easily get at but didn't need to be in the trailer.
Also, make sure to turn things off at home, give someone a key to check on things, stop the mail, make sure a neighbor is picking up the stupid flyers that get thrown on your lawn and cutting the grass.....
My best advice would be don't push yourself too hard, take the time to really see all that landscape you're driving by, it's a beautiful country.
2017 JayFlight 23RB
2007 Totoya Tundra Crew Cab 5.7L V8
Me, DH, DS x 2