Although the CEL might indicate a bad or failing O2 sensor, I would not just throw parts at the car. There are four O2 sensors, and each cost in the vicinity of $50-$75.
Also, there are hundreds of things that a CEL can indicate. You could have a loose gas cap, a loose or broken vacuum hose, an EGR system problem, bad spark plugs, etc.
You need to get the code read in order for any real help. I hear that Autozone will read the CEL for free.
Once you get the correct CEL #, you can search the CEG forums for an answer or post a new question.
