How old is your house? I tried to remove wallpaper in the hall of our Victorian terrace, and found that huge chunks of the old grey plaster came away with it! In the end, because I couldn't face getting the whole hall replastered, we patch-plastered the holes we'd made, left the rest of the wallpaper alone, and painted over it. Not ideal, but pragmatic!
1. No, not on walls unless it's a really bright colour and won't cover well.
2. Potentially a big job. Chances are the plaster underneath won't be smooth enough for painting. you could always take it off and see what it's like, then either re paper or get walls skimmed (more expensive).
I may be painting my house this weekend and would like help with two things...
Do I NEED a primer/undercoat to paint over already painted walls?
I am thinking of stripping the wallpaper in the living room that has just been painted over but will this be a massive job? I am afraid after taking the wallpaper away the walls will be too bad to paint and leave holes etc.. but on other hands the wallpaper atm is all bubbly and i want nice flat walls!