I forget the keyseq to kill X. It's something like CTRL-SHIFT-BACKSPACE or CTRL-ALT-BACKSPACE. Do that and then you can download the nvidia drivers using lynx and install them from bash.
As for the missing screen resolutions you have to edit your xorg.conf (i think that's what Ubuntu probably uses). It'll have a section along the lines of:
Subsection "Display"
Depth 24
Modes "1024x768" "800x600" "640x480"
EndSubsection
Just add the resolution to the front of the "Modes" line. In X type CTRL-SHIFT-+/- to change resolutions, I think.
Also try the nvidia forums and
http://www.linuxquestions.org/.
I haven't used linux in too long, I used to know this shit by heart.
Oh, I get it a screen from the 80's. If you type 'echo $SHELL' and hit enter does it say something like '/bin/bash'?
(woot, my UA unix account is still active!)
If so, type 'lynx http://www.nvidia.com/'. Navigate to the drivers and download them using the arrow-keys; up and down to select links, right and left to go forward and back. Q will quit.
Back at the shell type 'sh ' and the name of the file you downloaded. Follow the instructions. It should leave a readme in the directory you executed the file in. Read it. Do what it says, which should be something along the lines of open your xorg.conf (use something like pico, or joe unless you already know vim or emacs) and change some lines.
Um...I hope that helps.