The amount of supers you need per hive depends on season and location. As for replacing anything, unless you break it when you extract you shouldn't have to replace it. The whole purpose of the frames are to be able to extract the honey and reuse the frame with the comb intact. Also, if you know any local beekeepers (at the association perhaps) they are usually willing to "loan" you an extracter either for free or at a very reduced cost.