to remove your stock exhaust, jack the car up, make sure it is stable and secure. Move under it and undo the bolts holding it to the downpipe, and separate the two so that they are free to move inependantly while still hanging from the car. Then twist the end of the exhaust pipe which connected to the DP toward the passenger side of the car, and the forwad rubber mounting will come off. Then lift it up, and releive the tension on the rear hangars near the tip of the exhaust, and it will come right off.
To install, bolt the Blitz exhaust loosely to the Dp, then place the hangars on. Once it is on snugly, tighten the bolts connecting it to the DP. "hanging" the exhaust first may lead to problems as you try to pull the two ends of the DP and the exhaust into line to slip bolts through their flanges. I found this out the hard way.
Once you get under there, you'll see it is quite simple.