From my understanding, you are unlikely to be VAC banned for using rank/stats hacks (as long as you follow the maker's instructions carefully); I've yet to find a case whereby someone gets banned solely based on rank/stats hack. However, those who make outrageous changes will likely get their stats reset.
On the other hand, using aimbots, wallhacks and other hacks of this sort will likely get you a VAC ban sooner or later.