Ok, I read it up a bit and apparently the Botox blocks only the signal from the nerve to the muscle - so the nerve itself is unaffected and healing should be no problem. Of course using it in areas that are to be surgically changed may be not the best idea - not sure how well surgeons can account for that - on the other hand they only change the bone structure, the muscles are a different thing, right? So even if I have more or less wrinkles on the forehead or if I have more or less massetter muscle, the adjustments to the bone would be the same in either case.
I am kind of planning to give that massetter muscle botox a try, since I have bruxism anyways and it would be a double win if it solves that for a while plus improving my face.