How to change desktop environment or get a login screen from grub?

SUSE 13.1, KDE 4.11
So I was messing around and "accidentally" changed my desktop environment from KDE to Metacity. It's related to updating my NVidia driver, but that's a separate issue. I have my login set up to bypass the login screen and go straight to desktop, but after uninstalling the video driver it went to the login screen, where I clicked on the configuration icon and switched to Metacity.
Well, stupid me.
Now I can't figure out how to switch back. When it boots into Metacity, I just get a mouse pointer and an unresponsive black window...no surprises there. Ideally, I'd like to go back to the login screen and change the configuration back to KDE, but I have it set up to bypass the login screen. I can drop to a runlevel 3 shell, but no idea what to do there. I can probably edit a configuration file somewhere and change it back, but which one?
Is there a way to prompt a login screen from grub?
Probably a really easy solution to this one, but I can't find anything on google, and I've exhausted all ideas I have on it.
Help is appreciated. Thanks!