How do you replace a 2003 Buick Rendevous thermostat?

To replace the thermostat in a 2003 Buick Rendezvous, start by ensuring the engine is cool, then disconnect the negative battery cable. Drain the coolant, and remove the upper radiator hose connected to the thermostat housing. Unbolt the thermostat housing, take out the old thermostat, and install the new one with a new gasket. Reassemble by reversing the steps, refill the coolant, and reconnect the battery.