Work it free in the same manner as the tailpipe. We also wedged a screwdriver between the insulator and the bulkhead so that both people would have their hands free to yank the muffler around. Here are the flanges. That stock muffler is heavy. Try not to let them land on your noggin.
Assembly is reverse of disassembly.
Check the flanges for fit by sliding them over the flange studs. One of ours wasn't drilled right. If you have this problem, a few minutes with a rat-tail file should do the trick. Slide the flanges onto the inlet pipes. The flat side of the flange goes toward the catalytic converter.