The PITA part of the squared rings is that the hanger hook is slightly bigger than the opening of the ring, coupled with the structure of the squared ring, which makes it difficult to stretch. Hot water is a good trick for hard to stretch items. I ended up needing to use two stout (yet small) flat tip drivers to pry the ring into place, basically a wrestling match between me and the rings.
While you are in the process of tightening up the exhaust system, I would also suggest replacing the exhaust bushings. Those are the two rubber mounts (and bolts) on the bracket that runs from the exhaust pipe(s) to the tranny. Cost is something like $14.00 at the stealer. Bushing kit includes: new rubbers, new bolts and a new double U-bolt to attach the bracket to the pipe(s).
The rear muffler O rings are a piece of cake.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.