Says its overheating on 1994 Chevrolet Corsica

Our corsica says its overheating from what the thermostat gauge says. We can find no problem to it, as the engine does not even feel hot. We switched relays, the fan blows, nothing leaks. The only thing we haven't check is the thermostat as we have no clue how to get to it.

Any help?

Asked by for the 1994 Chevrolet Corsica
I would check your gauge. If the motor feels like it is not even warm, then it could either be the gauge or the sending unit for the gauge. which now a days is the coolant temp sensor. Any Service Engine Soon Lights on?
Nope, no service engine lights are on. Looked for the gauge in the book, going to check it out today.

10/21/09 - We changed the sensor and it went down to cold. However we noticed it went right back up to saying it hot again. It runs, we drove it. Didnt have any problems. Just can't figure out why it keeps saying its overheating when its not.