If you are looking for the engine temp switch(sending unit, it is located on the engine next to the large coolant hose (the hose that is not attached to the pump) on the engine. Just a little above and to the passenger side of the vehicle

I know the temp sensor is located on the engine usually near the upper radiator hose connection point but I don't have the exact location so I will defer to Brain Soufane's answer for that. It is not hard to replace, disconnect the wiring harness from it and unscrew it and screw the new one in.