Here's the link to the best 722 tranny manual I have found:
http://w126.pp.ru/akp722.pdf

My reverse started clicking and engaging slowly in reverse, and indeed it was just the reverse clutch plates. I did find plate material trapped in the filter when I cut it open.

The rest of my tranny was working fine, so, since I was doing the R&R myself I opted to just go far enough into the tranny to replace the reverse plates.
Getting that far is really pretty easy, and no special tools required.
Only problem was getting the band spring back in - you have to push hard and turn the plug screw at the same time - a little ingenuity with a large wrench as a lever got it done. I found no residue in the tranny other than in the filter, so I just buttoned her back up, and all was good again.

DG