Whenever I try to change a certain race's head or any other Face Data, an error pops up saying I have an "Invalid Directory". I used BSA Commander to unpack the files into "bsacmdr/out", I don't know if this is the problem, as I have no idea what a directory is. If anyone can help, it would be a pleasure, because I am looking forward to making more races. That's about all the information I have.

"Directory" in layman's terms is the technical name for "folder". There were no "folders" in the computer science courses I visited so far.
The CS will complain, if you try to point it to resource files "outside" of the game's data folder. I don't know where exactly your "bsacmdr/out" folders are located, but from the game's point of view that folder alone is not the proper place for its resource files already to begin with. Meshes (NIF files) have to reside somewhere inside the one-and-only "meshes" folder, textures inside "textures", and other files inside their respective designated folders as well.

Think of it this way. If you're going to release your stuff for others to use, where should they place your files for your plugin to find them? They won't have your folder "program files/xyz-folder/abc-subfolder" on their drives. The only folder structure you all will have in common is "oblivion/data/meshes" / "oblivion/data/textures" etc. And this is exactly where the CS is expecting the resource files to be located.

Blech. Forget what I said earlier. So, put all of the unpacked NIF mesh files into meshes, etc. Then, make and edit races, save as .esp, and hooray.

Exactly.
For convenience's sake stick to the existing folder structure and place your own stuff into your own subfolders.
For example, heads and other meshes from races usually will be found somewhere like "meshes/characters/{folder of your race}/".
It's best to stick to this scheme as I don't know what other factors the CS will also check for regarding such files' locations.