How do you replace a heater core on a 2001 Buick lesabre?

To replace the heater core on a 2001 Buick LeSabre, first, disconnect the battery and drain the coolant from the radiator. Remove the dashboard and the center console to access the HVAC unit, then disconnect the heater core hoses and remove the mounting screws. Take out the old heater core and install the new one, reassemble everything in reverse order, and refill the cooling system with coolant. Ensure to check for leaks and proper operation before finalizing the installation.