I've searched up a few other topics about decompiling portal2 models and player models, but none seemed to have very conclusive results. The question I'd like to ask is: is it possible to fully decompile the Chell player model so I can modify it, then recompile it? Mostly what I'd like to do is modify the face slightly, the tied top jumpsuit, and hair. Also, I have the gmod 13 chell model in gmod, so if needed I can use that to reconstruct broken pieces.

I don't think it will be possible--the more joints a model has, the worse it's mangled by the decompiler. I don't know if you'll even get a usable SMD out of Chell.

You will get a useable Chell SMD.
How to decompile a Portal 2 model is explained here: http://www.erikszeug.de/index.php?mc=po ... ecompiling

Okay thank you I got the model decompiled, and I made some changes. Also I noticed that there were some issues with the right shoulder, some missing vertices and such. Anyway, now the issue is StudioCompiler-GUI.exe. It will not for anything generate any files, usable or not. It just brings up a copy of the window which turns white and freezes up.

Try my little StudioMDL-GUI http://www.erikszeug.de/files/Programmi ... DL-GUI.exe .
Once it's done (or not) it will list all errors. Then take a look at them or post them here if you can't find out whats wrong.