You've got it right. Yes you can do this to the autoheat. I did this about two months ago. The auto heat only controls the operation of the flapper boxes.
Everything is pretty straight forward. Check here
Backdate .
You can also do a search in the archieves on my name. I had some good discussions.
I would suggest getting the parts used; easy, less time, and cheaper than the dealer.
Once you get the parts, just look at the engine bay. The only really tricky part is the left side scoop assembly. It's like a jigsaw puzzle.