My wife and I are going through the same thing with our unit. For the walls she lightly sanded them then used a oil based primer and painted them. As for you since you pulled most of your wall covering then I would say go with wall paper, because you have somewhat bare luan now and would take a lot of work to get it ready for paint. As for window coverings, she cleaned the blinds that were there and dyed some of the original curtains, and replaced/made some of the other curtains with material from wallmart. To get them to hang in the RV type curtain holder she cut off the top edge of the original curtain and sowed it to the new material. She recovered the valances with a new materail as well as the panels for the sides of the walk through from cab to RV.
I said "she" alot because the interior was all her except for the floor, she picked it out and I installed it. lol My job is all the mechanicals.
Good luck your off to a great start. just remember for everything you touch you uncover two things that still need to be done!!