You can paint over wallpaper assuming that it is well adhered to the wall, in particular the seams edges and corners. Run a light coat of drywall compound down each seam and smooth it with a damp sponge, don't try to sand it. A good quality primer sealer is required before the finish coats. Bear in mind that any raised pattern on the wallpaper will show through the paint.
I would spend the time to do it once properly and remove it, fill any areas that need it and sand smooth. It is worth it in the long term.