get a videotape on installing drywall (may be labeled as installing drywall). This will give you very explicit step-by-step instructions on the mudding and sanding aspect. (A friend of mine found it at Borders, which is one of those huge chain bookstores, but you might be able to find it at your public library. He had never done anything like this; he just followed the instructions precisely, and it looks perfect.) After you have finished this part of the project, there is a product made by Zinsser called Shieldz. It purports to be made specifically for sealing and priming over wallpaper in preparation for painting. I have never used it personally, so I cannot vouch for its effectiveness. I just know I ran across it when I was looking for primer for my plaster walls. Good luck.