Hello people! Newbie here. Hope you can help me out with some advice.
I'm looking at buying a 98 Cavalier RS with the 2.2 engine. It's done 94k miles and the check engine light is on. I'm guessing O2 sensor but the owner says it gets through spark plugs quickly.

Could these two issues be related?

If it's not the O2 sensor(s) any ideas what else it could be?

Possibly. Go to the local parts store and ask if they have a code-reader available. It could be that the manifold o2 sensor is done for, and causing the engine to run rich, which will foul out spark plugs. Its a fairly easy fix, and only costs around $50 for a new sensor. Your best bet is to just have the code read anf find out, rather than replacing a bunch of parts trying to fix the problem.

Thanks for the tip. You don't happen to know the codes for O2 sensor faults, do you?

Heres a link to a listing of all the DTC's, or diagnostic trouble codes:
DTC's