The duct circled in blue should pull off the housing. You may be able to see the door and reach it?
All doors are shown in the Distribution Housing. The manual still wants the HVAC assembly to be removed from the car to service these, but look it over for a short-cut? Perhaps there is a hack like the heater core that will save you time?
If installing a screw to hold things, make sure that it doesn't pierce the evaporator or heater core.
One thing that disturbs me is that the parts folder doesn't show the doors being available separately. Maybe they are only serviced by replacing the Air Distribution Assembly? Clarify this with a dealer parts counter-person?
The ADH is currently on backorder, with a possible release date of 1/9? Avg weekly demand is 8 units.
