Help with heat door in heater box (under dash)

[crazy_canadian]

I don't know how exactly it's called, but the door that controls the temperature of the air had broke.
The cables are now moving freely, and as far as I can tell, the red knob over the box still moves.
The button on the dash was hard to turn, and since tuesday I just get cold air in the truck.

Do I need to remove the whole dash to replace/repair it ?
I have borrowed the 1994 shop manual from the Ford dealer, but lacking the name of the name, I can't find it anywhere.
Dealer gave me the part number F5TZ-18A484-A, an obsolete part, can't find any info on that.

Thanks!

[96F350KID]

You check the end of the door acuator? i mean if you take it off can you move the door with your fingers or is the little tab it fits into gone?