I extracted all the necessary files, meshes and all that, to a folder. When I open the folder on its own, everything appears to have extracted just fine. When I try to select a model in GECK from that file, the BSP and NIFs and BSAs aren't showing up.

Why am I only able to browse files anyways? Why can't I just copy and paste the file path from one weapon and paste it into the new weapon?

nevermind, fix'd

I too wish we could just copy and paste path links. I've been tempted at times to just put a blank text file there with the appropriate name long enough to get the right filename in place, then remove it, but in the end I usually just extract the mesh I need.

You need to fully extract all the content from the BSA files. Or, duplicate an item that uses the model you want. Though if you are going to do any lengthy modding, you are better off just extracting everything.