Removing the wallpaper now won't be easy since it is sealed by paint. Plan on causing some damage that will need patching, it's inevitable. You will need a couple of tools to get this done.
1) A paper tiger. This is a round hand held tool that will put small holes in the wallpaper to help or allow wallpaper remover to soak into the paper.
2) A 3-4 inch stiff chisel edge putty knife to scrape off the paper.
First, perforate the paper with small holes trying to minimize any damage to the underlying wall. This could be somewhat difficult. Now apply a wallpaper stripper keeping the surface wet for 30 minutes.
After this time start peeling away the top layer of painted paper. Once this is done apply more stripper and repeat. Keep applying the wallpaper stripper, allow to soak and loosen some paper then scrape off.
Some areas could come off easily while other areas will fight. Once all of the paper is removed do a final rinse/washing with fresh water and allow to dry before priming and patching.