The exhaust is very easy to take off as long as you have a basic set of wrenches. Best way to separate the muffler from the pipe IMO is to take the whole exhaust system off then do the squeeze and wiggle method mentioned above. I used a little liquid wrench and had a second person help pull to separate them This should also help prevent damaging the gasket.
As for the backfire pops, that's totally normal with a stock bike. It's not detrimental in any way and is caused from running lean, its just that the bike isn't tuned as good as it could be. From what I've heard it's tough to completely eliminate backfire on the stock setup, some claim they have, others say they can get it down to a slight 'sputtering' sound. I've pretty much eliminated the back fire on mine, I added a Dyna Muffler, re jetted, and did a slight adjustment to the idle mixture screw. My bike still has that slight sputter and feel when deacceling, but it sounds healthy and normal, I would imagine it's just our big 650 single cylinder engine letting us know it's a Thumper and not a V-Twin.
As for the leaks described above, they are speaking about an exhaust leak. This means somewhere in your exhaust system exhaust fumes are leaking out at some place other than the end of the muffler. This will cause popping and back firing as well. You can generally find these by feeling around where the exhaust goes into the head of the engine or at the exhaust joint where it joins the muffler. If you feel puffs of air coming out, you have a leak. I believe there is also a 'candle method' that is more precise than the hand method. Make sure you don't burn yourself and good luck!