Here's how I fixed my blend door.
The recess in the blend door that the actuator motor shaft engages is deeper than the shaft reaches. My blend door still had some undamaged hole depth left in it. So I made an extension for the actuator shaft so it could reach the undamaged part of the hole and move the door.
This extension is made from 3/8" aluminum rod, 15/32" long. I drilled and tapped the center of the end of it to take a piece of 2-56 threaded rod. A bit bigger would be better, but that's what I had on hand. Then I filed and belt sanded the extension to match the "D" shape of the actuator shaft. It has to taper down quite a bit to fit into the door hole, which has a taper. You can see this with a mirror.
To keep the extension from rotating out of alignment, I made matching shallow razor saw cuts in the ends of the shaft and extension and upon assembly, inserted a small piece of thin sheet metal in the cuts to lock them into alignment.
I failed to measure the length of the threaded rod I used. I just made it long enough to stick out the top of the actuator shaft (it's hollow) far enough to get a washer and 2 nuts on it. (jamnut)
I used loctite where the rod screws into the extension and epoxy where the shaft and extension join to keep that little piece of sheetmetal in place and for additional strength.
I'm hoping this will make a permanent repair because the material at the bottom of the hole is thicker than at the top, so maybe it won't break.
See my gallery for pictures. Sorry the pictures are so bad. My camera won't focus very close.
If any of this isn't clear, say so and I will try to clarify it.