Can you paint over dark wallpaper and what kind of paint should I use?

Depends on the quality of the wallpaper and how well it is stuck to the wall... some will separate from the backing when they get wet and paint is wet and will soak into the paper... try it on a small area...and see how it drys and how hard it is to cover.

It seems like the fastest and easiest thing to do but having done it I would recommend that you strip the wallpaper and then paint. You'll probably be able to see the seams through the paint.

If you're dead set on doing this then use oil based paint because latex paint will make the wallpaper release from the wall. From my experience.

Stick down any loose before washing the walls with a mild detergent, rinse with clean water and let dry thoroughly. Depending on your surface, you may need to use an undercoat. If you are painting onto vinyl wallpaper, you will need a coat of Multi-Surface Primer to create a base for the paint to sit on.

If you put water on wallpaper it will start to come off.

That is the way you would remove wallpaper. Everything I've read says use oil based primer so it won't wet the glue.

Yes, you can paint over wallpaper. If it is paper it will absorb moisture from a waterbased primer and reactivate (loosen) the glue, so it is best to use an oilbased primer. The oilbased products of today don't stink like they did in the old days.