How do you replace the heater core in a 2002 Buick LeSabre?

To replace the heater core in a 2002 Buick LeSabre, first disconnect the battery and drain the coolant from the radiator. Next, remove the dashboard and the heater assembly to access the heater core, which is located inside the vehicle. Disconnect the hoses and any mounting screws, then carefully remove the old heater core and install the new one. Reassemble the dashboard and heater assembly, refill the coolant, and reconnect the battery.