Check engine light on. Auto Zone diagnosed and said it was the coolant sensor. on 2002 Saturn SL1

How do I replace the $10.82 censor. I just bought this car used on Thursday 2002 Saturn and the Owner's handbook is not complete. Missing the repair portion.

Asked by for the 2002 Saturn SL1
There is no repair section in the owners manual. Also, most Saturns will need a new thermostat with a coolant sensor code, at least that is how many I have done have worked out. You might think about having a shop really inspect the car, the AZ guys mean well, but they aren't mechanics.