How do you replace the thermostat located on a 2002 Mazda Protege?

To replace the thermostat on a 2002 Mazda Protege, first, ensure the engine is cool and disconnect the negative battery terminal. Drain the coolant from the radiator, then remove the upper radiator hose and the thermostat housing. Take out the old thermostat, clean the mating surfaces, and install the new thermostat with the correct orientation. Reassemble the housing, reconnect the hose, refill the coolant, and check for leaks after starting the engine.