Final update,
I didn't mention in my OP that the muffler was one of the reasons the motorhome failed a state inspection so I was compelled to deal with it. As previously stated I managed to get everything I needed from Amazon and my local parts store and the updated total cost is about 400.00 which is about a 600.00 savings over what the shop was going to charge. When I had everything removed I carefully checked the muffler for the whole I was told was there. Lo and behold there was none, just a glitch in the seam weld that was not letting any exhaust escape. In the end all I really should have had to get was a couple of straps, and an elbow at the outlet. Not sure whether an honest mistake was made or they intended to sell me something I didn't need. I took it in and got it rechecked and the inspection sticker. I told the manager that there was no hole but he wasn't very helpful and didn't want to hear it. Not sure how far I'll take it but for sure they won't get another cent of my business.