If you remove any undercover from the drivers end of the dash board, remove the air duct under the column area and look at the end of the HVAC box you will see the blend door motor. The motor is about 2 x 3 inches and 1 inch thick. Remove the electrical connection and the screws that secure the motor to the case and pull the motor off the door shaft.
Let me know how much detail and the answers to my questions above and I will be happy to help you with this
Unless you have dual temperature controls you have a single actuator that may be the issue or the door itself may be broken.
Find the actuator at the drivers end of the HVAC box as I outlined above and remove the motor. Run the system and see if you can rotate the door with the stub of the door shaft that the motor turns. If you can control the temp this way you only have to replace the motor, if you cannot turn the door and control the temp the entire dash will have to be rolled back so the HVAC box can be removed to open it and replace the door.
The diagram of the HVAC case with the location of the motor is below, there is not a lot of documentation about this procedure so you will have to work with me to tell me what you don't understand about what I am telling you and what you are seeing.
A view of the single door controls is below to be sure we are on the same page
Look these over and let me know what you need from me about removing the motor