How do you install a heater assembly in a 1998 Lexus GS 400?

To install a heater assembly in a 1998 Lexus GS 400, first, disconnect the battery and drain the cooling system. Remove the dashboard and any necessary components to access the heater core. Then, detach the old heater assembly from the vehicle and install the new one, ensuring all hoses and connections are secure. Finally, reassemble the dashboard, refill the cooling system, and reconnect the battery.