Thanks and here's my followup
Just fixed my bad actuator due to this awesome post.
Here's my input:
Initially, I wasn't sure how to remove the large black cover to remove the final screw. I was worried about breaking the plastic when trying to pry it off the motor body. Just work it slowly, but you should see how it the plastic is "keyed" into the motor body plastic.
Once the cover is off and the final screw is removed: there are 3 items to watch out for during reassembly.
The first obvious part is the cable which slips into a little plastic arm protruding from the actuator body. That's easy.
The other two are adjacent to each other. There's a ball-joint style mechanism (cupped-u that fits into a ball). That's easy to fit together as it has a lot of play.
The final thing is subtle: just a protruded peice of plastic which then fits into a hole in some metal fixture. That locates the two peices; without this mated up properly the ball tends to fall out of the u-cup quite easily.
Once you reassembled those 3 items, you put in a screw to hold them together. Then you can put the cover back on. But the entire assembly will loosely sit on top of each other. Line up the bodies properly so the bottom two screw holes are both center aligned, then drive in the final 2 screws. Now it's complete!
Pull the rods and the cables to test your assembly out. It should feel right.
Now on to the Mabuchi motor. I could not find a motor with a flat shaft on eBay (even though it was reported to be the case) So I wound up just dismantling the old and new motor and swapping the shafts. So old shaft goes into the new body. It worked just fine for me. I suppose you could try swapping the brushes themselves out, but this seemed like an easier approach.