Blend door -passenger side
 

Avalanche 04' with dual heater controls. On vent setting the passenger side blows hot for quit a while until (i'm guessing) the blend door finally swings shut. Either the door is sticking or the actuator is bad (I'm guessing again). How do I get to the door and actuator? is it a major job? Is the actuator an electric motor or vacuum deal?
Thanks

Joe B