I have a 1984 300D Turbo Diesel, which is quite nice, but no air comes out my center vents no matter what mode the climate control system is in. I believe the culprit is the Center Vent Vacuum Pod, but I have seen many methods for getting at this and would like to know the "best" way to attack or test it without having to remove the dash. I am fairly new to working on cars in general, but I would like to give it a go (maybe replacing that door lock gave me a false sense of confidence

).
Thanks in advance for any help you might offer.
EDIT: Found where I can buy the pod, quite well hidden...