gedit requires xorg, so you can't run it from a console. try nano.
Originally Posted by Brightbelt
Or you can just start things from the keyboard if you know the shortcuts
ALT+F2 opens the "Run Application" dialog. you can start whatever you want from there (gnome-terminal, or even just gedit)
The easiest way to backup your file is to make a copy before making changes:
Then if you need to copy it back,
sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
sudo cp /etc/X11/xorg.conf.bak /etc/X11/xorg.conf