Muffler replacement is a rather simple task and there is plenty of room to do so on the TB platform. From the factory they are welded, but even if they were clamped it would take a cutting tool of some sort to remove the pipes as they tend to virtually weld themselves together after time and miles.
Generally, if the pipe leading into the muffler is good, I would just cut it as close to the muffler as possible. That can be done with a hack saw, cut-off wheel, sawsall, or a specialty muffler tubing cutter (make sure the one you get goes big enough -- the TB uses a rather LARGE size exhaust tubing!).
http://www.amazon.com/GearWrench-2031DD-Exhaust-Tailpipe-Cutter/dp/B000M93OUM/ref=pd_sbs_auto_1?ie=UTF8&refRID=0AGPN5GX6EPRAQ1Q3WPT
Next comes the replacement muffler. Some guys have spent a LOT of money trying to make the TB with the inline, double-overhead-cam 6 cylinder sound good with a rumble. So far NO ONE has succeeded. They get louder and "ricey" sounding but due to the nature of the engine design itself, they will never "rumble" like a nice v-8. So, take care with muffler selection as you can end up with a vehicle that is a pain in the ear...
You may need to stub on a section of pipe to the rear of the muffler if you are replacing the factory muffler with one that is smaller. They can be clamped or welded in place.
This may help you to know what you are looking at:
