How do you replace a 1998 Mitsubishi diamante thermostat?

To replace the thermostat on a 1998 Mitsubishi Diamante, first, ensure the engine is cool and disconnect the negative battery terminal. Drain the coolant from the radiator and remove the upper radiator hose to access the thermostat housing. Unscrew the housing, take out the old thermostat, clean the mating surfaces, and install the new thermostat with the correct orientation. Finally, reassemble everything, refill the coolant, and reconnect the battery.