So after telling Debian to just update some packages across the board, it proceeded to shred itself. Either something went haywire or it opted to grab packages off unstable/testing - I'm not sure.

Anyway, it's well and truly screwed up; GDM is screwed, my Nvidia display drivers are messed up, basically half or more of the OS is being pretty unhappy.

It still runs on a command line.

I figure I'll just reinstall everything fresh, won't really lose anything I can't have repaired in an hour. Is there any way to do this without an install CD, or to somehow revert the whole shebang back to original install specs?

Seems like there would be, but I never got that far experientially.

Appreciate whatever help you guys and gals can provide, 'cause I won't be able to burn a new installer CD for a month at least, but want to get it working properly.

you could create a new xorg.conf file using the xorgcfg (or something similar) command and i am sure your display will come back to normal.
post exact errors.

Was trashed a lot worse than that, unfortunately. Got lucky and found a blank CD, reinstalled from scratch. Far as I can tell packages got mixed up pretty badly; it wouldn't even make an attempt to install/reinstall stuff.

Now I'm back to the usual problem of how xserver hates me, my mouse, and likes to scream "VRAAAAGH!" much of the time.

C'est la vie.