How difficult is it to change out the wallpaper in a TT?

The wallboard comes with a pattern on it, you would have to paper over it. Try a small area because it may have a light finish on it that could prevent paper from sticking. The wallpaper border that is in quite a few RV's, I would be very careful trying to remove it. You could damage the wallboard. I would also think about when you tire of the new paper, how are you going to remove it without any damage? ?//

It isn't wallpaper.
It is paneling with the pattern bonded to it from the factory.
You cannot peel it off to change it. All you can do is cover it up with something else.