FYI..This is from the top of my head but it should be close..
When you reboot highlight your boot option and hit
e , then go to the line that has the
kernel or
root=label=/ line and hit
e and add
3 (that is spacebar 3)to the end (should look something like this
root=label=/ 3), then hit
enter then
b This should boot you into init 3 level and no GUI
My 2