Remove the sound insulator panel under the passenger side dash. Remove the glove compartment from the dash to access the temperature actuator (5).
Sounds like you got some misinformation from the dealer. The mode acutator changes air delivery modes from floor to vent to defrost. The air inlet actuator changes the air inlet from recirculate mode to fresh air mode. The problem is the drivers side temperature actuator if the drivers side will not get warm.
This actuator is located on the drivers side of the a/c case and can be accessed from under the drivers side dash. The actuator is near the area of the accelerator pedal.