How do you replace thermostat in a 2002 Isuzu Rodeo?

To replace the thermostat in a 2002 Isuzu Rodeo, first ensure the engine is cool, then disconnect the negative battery cable. Drain the coolant from the radiator and remove the upper radiator hose connected to the thermostat housing. Unscrew the thermostat housing, take out the old thermostat, and clean the mating surfaces before installing the new thermostat and gasket. Reassemble everything, refill the coolant, and reconnect the battery.