we're about to paint the interior of our coach as well (a 2004 Damon Challenger)
My research and experience with other projects leads me to believe that I should clean and give a good scrub and then use a shellac-based primer (one popular brand I use often is Zinsser) Shellac will stick to just about anything and just about anything will then stick to shellac... After the prime, I plan to paint with interior-grade house paint.
I've got a piece of wallboard from my wardrobe removal that has the paper on it and I'll be doing some test strips first and will let y'all know how it goes.
Lawrence