My wife drives a 2010 Armada Platinum 4wd and about 6 months ago we started hearing a loud knocking sound coming from under the dash in the middle to right side of the dash. It is fairly random, but noticed it having trouble changing between cold and hot air. Last week the noise stopped and now I can’t get heat to come out of the front vents, but the rear heat works normal. I assume it’s the blend door actuator? Took it by a shop and they said the dash would need to be removed to fix it and they quoted me $623. I called the dealership and they quoted me $1,250. So I assume there’s no trick way to replace this actuator without taking out the dash? Does $623 should reasonable?