Hi,
Hopefully you've got a resolution to your problem since it's been a while, but I didn't see any replies so here goes.

1. I don't know

2. I took mine out of the Lightweight a few years ago, had a bearing fail so rebuilt wiht new instead of forking out for a replacement unit. If i recall, it's a simple process; remove the cable by unscrewing and disconnecting. then loosen and disconnect the bolt used to adjust the belt tension, finally there should be a bolt on the bottom used as a pivot for the tension, pull this and lift out the gen. It is heavy so beware

3. I've not had the brushes done or anyone else work on the gen. but I did need the starter motor to be rebuilt at one point, I simply took it to an auto-electrician that specialized in 24v. commercial vehicles and RVs


Hope my limited knowledge helps, and that the truck is running well

Jon