[MrE]

I would make some phone calls before I authorized any muffler repairs. The first call would be to Newell, and I'm assuming that they will confirm your suspicion that you can cut the old one off and weld a new one on. If that is the case I would get on the phone with shops that specialize in truck/bus mufflers and get a quote. Sounds like the Cat shop is running out of work and hoping you'll help them out.