I got everything back in, and it all spins like it's supposed to.

There was lots of interference between gears and it was generally a pretty big hassle. A big enough hassle that when I started and everything was going smooth I was thinking that this was a pretty easy job, but now I wouldn't really want to do it again. I didn't replace any of the seals, or the o-ring, so I probably will have to do it again at some point. I'll update with photos later (which will look the same as every other photo so far), but right now it's late.