Also good to check the coil.
Get the code scanned (it should store a code IIRC) to determine which cylinder it is. Autozone or JVT is your ticket.
The in-laws had a misfire CEL on their 96 Bonneville and I had to replace a plug wire (high resistance) as well as an individual coil (also high resistance). Nice thing about GM coil packs is that you can swap individual coils, instead of the whole set like ours.
