Disconnect negative battery cable. Drain cooling system.
Remove instrument panel.
In engine compartment, disconnect heater hoses and plug all openings. Remove 4 heater assembly nuts from engine compartment firewall. Inside vehicle, remove heater assembly support brace screw, and swing support brace out of way. Move passenger seat rearward.
Carefully pull heater assembly rearward until studs and heater core tubes clear firewall. Lower heater assembly and rotate assembly until studs are facing downward. Remove heater assembly from vehicle.
Place heater assembly on work bench with assembly housing cover facing down. Remove 2 bolts securing heater assembly housing cover to blower motor housing cover. Unplug vacuum harness connector from panel/defrost door actuator.
Remove floor duct from heater assembly housing. Remove 2 bolts securing heater assembly housing cover to lower housing near floor outlet. Turn assembly over. Disengage vacuum harness retainer and vacuum harness. Remove 13 screws securing housing cover.
Remove blend-air door lever. Gently pry panel-defrost door lever off. Pull up on heater assembly housing cover far enough to separate cover sealant and remove cover.