I just removed my baffle-piece of cake. It has been installed for about 2,500 miles and one year.
First I soaked the back end of the pipe where it was carboned up with solvent and then penetrating oil, then cleaned out as much carbon as I could with steel wool. Then I tried the pound it out with a 2X2, too small, so I cut a 2X4 to just fit inside the front of the pipe, laid the muffler down on a few towels on the work bench, and popped the baffle right out with a small sledge.
Now if I just had the replacement quiet baffle I'd be done.
I would say that the main problem would be trying to pound the baffle out without having cleaned out all the carbon, as it is a fairly tight fit in the barrel. Also having the maximum diameter piece of wood helps, as the baffles are sharp and a slightly smaller piece of wood will just get wedged in tighter and tighter as the baffles are sharp and will rasp off the corners of the wood.