My screen is messed up, cannot see anything.

I am using Ubuntu, which I downloaded and installed less than a month ago.

If you open the dialog that allows you to adjust the resolution ("appearance", I think), there is a tab that says "Effects" or something. There are 3 choices: None, normal, and all of them (I think). I wanted to see what cool effects there were (3D desktop?), so I clicked Normal (it was on NONE). It installed some drivers or something and then asked me to restart.

Now when I restart, the screen is all messed up! I can see the boot-up stuff, but everything from the log-in screen and on is just a blur or random lines. I know from adjusting the resolution in windows XP (I have a partition) that my monitor may have issues with some resolutions. Anyway, now I cannot even see what I am doing to undo what I did or lower the resolution. Can anybody tell me how to fix this from the recovery mode, or perhaps even the shortcut-keys to press to navigate to the dialog that will allow me undo it (blindly, assuming I press the right keys)? I suspect it may be my monitor, but I have to fix the problem somehow.

I am brand new to linux, so if you tell me to go into recovery mode and then copy this file here and move it there, I am going to be lost (unless you tell me what to type). I am seeing people talk about this /etc/x11/xorg.conf file, but (from recovery mode) it says there is no directory called x11.