How do you replace a heatercore in a 2001 Pontiac Montana?

To replace the heater core in a 2001 Pontiac Montana, start by disconnecting the battery and draining the coolant from the radiator. Remove the dashboard and center console to access the heater core, then disconnect the hoses and any electrical connections. Carefully remove the old heater core and install the new one, reassembling the components in reverse order. Finally, refill the coolant, check for leaks, and reconnect the battery.