What is the best way to fix the heaters act

It may be teh actuator not the door, if the door is broken off the shaft the dash has to come out then the heater
here are instructions for actuator removal
1. Disconnect negative battery cable. Remove right lower console trim panel from instrument panel. If equipped with center console,  remove right,  front side panel from console. Disconnect A/C electronic blend door HEATER/EVAPORATORÂ
actuator connector from actuator. EVAPORATOR CORE
2. Remove 4 screws retaining A/C electronic blend door actuator to heater/evaporator housing. Remove A/C electronic blend door actuator. See Fig. 7. To install,  reverse removal procedure.
If it’s the heater door
Heater box need to be removed, that’s done after removing dash board and cluster panel
If it’s the blend door actuator u can access it by removing the radio