Okay, thanks for the help earlier (I was using my wife +Allison Tucker
's phone to post for help since I couldn't). After some messing around I realized mobile data worked fine in the browser or elsewhere, I just couldn't use any Google app at all (G+, Gvoice, Gmessenger, GAllTheThings, etc) so I thought all data was down. I downloaded the gapps through Chrome and installed it, then had to go through setup.
This is why I was confused about why Gapps was needed. I thought 4.2 was so minor it was like a regular update, I didn't expect it to be a whole new OS install essentially (at least as far as the google apps are concerned).
Everything works now except GDrive keeps giving a "runtime exception" error in the notifications, though the app seems to work and Play Movies/TV keeps popping up saying it has stopped and the app wont work at all. Trying to search for a fix...