It's pretty self explanatory. Get under the back of the engine, spray the nuts liberally with penetrating fluid. I like PB Blaster. I suggest doing this a couple of times, driving the car in between to heat up the exhaust. Then, when you're ready to remove, spray again, while the pipe is warm. It will smoke, but won't burn. Use an air impact if you can. New gasket, new nuts. If you break a stud, you've got a lot more work involved. If you don't think a nut is going to release, stop, and get it to someone that has a torch setup.
Got it! Put it on last night! I used pb blaster, and a socket wrench. Also had to take off the axle shield, but I got it to work!! Here's the picture of the Downpipe I took of compared to the one I put on last night.