You can use Fallout Mod Manager to unpack the NIFs from the BSA if you want to edit them. You don't need to replace the files in the BSA in order to use a body replacer mesh though. You need to download Archive Invalidation Invalidated to prevent the BSA from overriding custom meshes and then place the body meshes and textures into appropriate subdirectories of the Fallout 3 data directory. On my computer the body meshes would go into D:\Fallout 3\Data\meshes\characters\_male. It is hard for me to believe that the documentation for these replacer files does not include this sort of information. I read the readme and directions pretty carefully, it says to replace the .nif with the new one, but I couldn't figure out how to do that without being able to modify the archive. I'm using FOMM and so far, I'm evidently not very bright, because I can't even seem to get it to recognize the MMM. Follwed the directions as well as I could, but since I'm new to using mods on Fallout, evidently I'm behind on the stuff "everyone knows". I'll keep screwing with it and see if I can get it to work. Thanks for your help anyway