Most of the time they have to pull the dash apart. 10 hour job. I know this is older Expies, but maybe worth looking at as an option...
I turned on our 2007 Ford Expedition Eddie Bauer yesterday and heard a distinct knocking in the dash. I previously replaced a blend door actuator in the rear of our 03 Expedition so new immediately the problem. I, however, did not know how to reach the actuator in the 07. I searched and searched and never did find a "how to" for my specific vehicle. I did find a tsb and a how to on how to remove the navigation and this is what I did:
1) There are two pieces of forward facing trim around the navigation/stero and the air controls. I removed the bottom piece first using a thin drywall joint knife. I started on the top right corner, then top left, then bottom. The piece came straight out.
2) I removed the top piece of trim in the same manner. Again it pulls straight out.
3) I unplugged the top two electrical inputs. I marked the right from the left, not that you could get them confused, and left the other electronics plugged in. I let the top trim dangle to the right of the center consol.
4) The navigation is held by 4 7mm bolt screws. I removed all four and pulled out the nav unit. I did not unplug the nav unit put placed it gently on the center consol.
5) The actuator was directly behind the Nav unit, slightly to the right. It was held by two 8mm bolts. I could not access the bolts with a ratchet, so I used a standard wrench. A little difficult to acces the back bolt, but not horrible.
6) Removed the actuator by pulling straight up, unplugged from electrical - a little tricky because there is a lock - push red thingy out then push black tab down, purchased a new actuator from NAPA for $45 and reinstalled.
Total time was approximately 40 minutes. The dealership quoted 6 hours and $800 dollars. Local mechanic wanted $450.