reverting to 'standard' etch installation

Folks, I made a cuckoo (mess up) - I had installed Etch from netinst and done the upgrades. That was a while ago. Last night I decided I wanted gnomad2 from unstable so amended my /etc/apt/sources.list and installed it (along with other dependencies, particularly I remember OO being removed/(re)installed). Now I seem to be having problems with gdm/X (non-responding). I think I'd prefer the stable Etch without gnomad2, but how do I easily "unroll" what I did last night? I'm happy to re-install Etch from the CD but is there a quicker way and anyway not to lose the data on the HD? Pointers to FAQs (surely I'm not the first!) are most welcome!

T.I.A.
Michael

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