How much damage you do to the wall depends on just where the existing wires are and what access you have. In my bathroom I was able to disconnect the old fixture and then go up in the attic and pull the wires to the old fixure out and rerun them down into the new location. The only thing I had to do to the wall is a small hole behind where the new fixtures were going (covered up by it) and patching and painting over the old fixture's hole. In fact, in one bathroom after a few years my wife redesigned and I went back and put it in the original location. The holes in the top plate of the wall (in the attic) were still there, so it was just a matter of reversing the process.

Thank you, ronnatalie!