Oil on spark plugs?
Either way.. if it's on the threads, I think that you just have an issue with your PCV system letting oil down into the cylinder..
Check into an AMW Catch Can -------->
Other than that..is the engine stock? If stock, how many miles on it? If the car has aftermarket heads it could be pulling some oil around the rocker studs. May need to put some silicone on the rocker stud threads. If every plug is oily it's more than likely PCV related.
http://www.hovis.cc/Firebird_HTML/pcv_mod.htm
a lot of info on what it is, how it works and one of the options to deal with it. If the probelm is serious, you will probably need a catch can.

