How do you replace a 2001 Chevy Cavalier O2 sensor?

The check engine light came on. I took it to a mechanic. They ran some diagnostics and replaced spark plugs and wires. I drove it around for a while and the check engine light came on again. This time the same mechanic's diagnostics said the O2 sensor needs to be replaced.



Is it possible to confuse the diagnostic results so that the plugs and wires were changed instead of the O2 sensor? In other words, do you think the mechanic is incompetent?



Is there only 1 O2 sensor on this particular car?



How difficult is it to change for someone who only does light maintenance on their car?How do you replace a 2001 Chevy Cavalier O2 sensor?
If you can get the car up, you should be able to change out the sensor. It's typically located pre-catalytic convertor, in the pipes (it has wires coming out of it...can't miss it). Grab the Hayne's Manual for your car. It'll tell you how many there are and where they are. I will say that it may be tough...all of that heat and expansion/contraction may make it difficult to move, so be ready for it.