How do you replace the heater core on a 93 Buick Regal 3.8L?

To replace the heater core on a 1993 Buick Regal with a 3.8L engine, first, disconnect the negative battery cable and drain the coolant from the radiator. Remove the dashboard and HVAC assembly to access the heater core, which typically involves taking out several screws and possibly disconnecting wiring harnesses. After removing the old heater core, install the new one, reassemble the HVAC unit and dashboard, and refill the cooling system with coolant before reconnecting the battery and testing for leaks. Always refer to a repair manual for specific details and torque specifications.