I was wondering being a semi linux noob, and have done so much trolling of the interet. If someone could help me speed up my testing of different things in xorg.conf. (using jaunty)

1) Is there a good method of testing (xorg.conf - gnome?) with out constantly rebooting?
2) If crap goes wrong like it often does, like locking up on entrance to gnome. Is there a way of bringing me back to command prompt. So that I can re edit xorg.conf and start gnome again. How to do that to from the command prompt?

I can read so if one does not want to take time answering this, a url will do. Thanks