How do you change oil pump on a 2002 Pontiac Montana?

To change the oil pump on a 2002 Pontiac Montana, start by disconnecting the negative battery cable and draining the engine oil. Remove the oil pan by unbolting it from the engine, which may require removing other components for access. Once the oil pan is off, detach the old oil pump from the engine block, install the new oil pump with a new gasket, and reassemble the oil pan. Finally, refill the engine with oil, reconnect the battery, and start the engine to check for leaks.