It's not that hard partner, it's a 2 1/2 inch muffler, center inlet, offset outlet. Not much to screw up. Look at the pictures on the website. Measure your original and make sure you don't buy one longer or thicker if you want offroad clearance. I put my FlowMaster all the way in the back when I cut the original out so that the rear wheels will ride up on obstacles before the muffler snags up, but you can do what you think best.
The original runs almost back to the bend in the pipe going over the axle. I kept in the original flange, others have cut it out and welded in eveything solid.
Have faith in yourself, you can't screw this thing up, or just go to a shop and have them order and install for about $120. $40 or so is the weld job.
Don't try to weld stainless mufflers to your steel pipes, get the steel one.