How do you change a thermostat on a Colorado with a 3.5?

To change the thermostat on a Colorado with a 3.5L engine, first ensure the engine is cool, then disconnect the negative battery cable. Remove the engine cover if applicable, and locate the thermostat housing. Drain some coolant to prevent spills, unbolt the housing, remove the old thermostat, and replace it with the new one, ensuring the gasket is aligned correctly. Reassemble the housing, refill the coolant, and reconnect the battery.