Not crazy. A thousand miles is not very far, do that several times a year (each way) to stay in touch with family.
A motorhome that old, I would be concerned about condition of tires and brakes. tires rot, braking systems corrode.
One of the problems with your destination (don't know about enroute) is that great sites for RVs and good sites for tent camping are not always in the same place. People with RVs use "campground" to mean "RV parking place with facilities" but they are really different kinds of facilities and not always located in the same place. You can learn to camp in a RV (giving up some of its home-like capabilities) and put it in a campground, but less often can you pitch tents in a RV park where the RV has full home-like functionality.
We visited, stayed at, Yellowstone long before there were any RV hookups, but our RV did not hook up anyway, except a 15 amp power cord. So the campgrounds were OK. Used the LPG lights and appliances in the trailer, some of us slept in the back of the station wagon. When the bears came snooping around, would not have wanted to be in a tent, it was crazy enough having them inspect us through the windows of the station wagon.
Bear management has since changed in Yellowstone, there is a RV park for RVs (no camping) and campgrounds where RVs can park (no hookups). You'll have to figure out what you want to do. The RV park needs reservations, the campgrounds are first come, first served.
I would not make 1000 miles the first trip. I would take a trial trip or two, not even an overnight, just a loop for a picnic or something. Back and forth to a local lake works. It is all about learning how things work, and learning what does not work, and fixing that, before making the first longer trip. I have a 100 mile loop, with a lunch stop, about a half day trip, that I used to first try out the RV, and use it to check things out at the beginning of the season sometimes, though I can also do it in camp driveway without spending $30-50 on gas.
Tom Test
Itasca Spirit 29B