I would think the answer is possibly a yes to the first question (removal) as the exhausts have to be removed, but only a possibly to the second part of Q1. They might have got away with not removing the bumper to remove the exhausts (they have to come off), but they will have had to be very careful!!
As far as Q2 goes, unlikely, but the exhaust and half the bottom of the car will have had to come off because of all the shields.
If you have a look at
this thread over on Xoutpost from 2010 it is for an aftermarket exhause fitting and clearly shows all of the under car shields in Post #2, and some shots of the rear underside in post 1.
If they didn't remove the bumper then there is a very high likelihood that as the exhaust MUST come off to change the rear diff system, they may well have damaged the car if suitable care wasn't taken. If they are the only ones who worked on the car, then it's down to them to repair/replace etc.
Richard