If the wallpaper won't come off with traditional methods, then I would go over it with a product called Nu-Wall. It goes on like wallpaper and gives you a tough skin that is flat like a ... wall! Not many people know about this stuff but it works very well and is easy to put up. The other thing you could do is get what is called paintable wallpaper. It is a thick wallpaper that hides what is underneath it. It looks good and you can get it locally. It's cheap too, $5 a roll.