if you have the donut gasket it helps. and make sure you clean all of the old one off.
the higher you can get the car the easier it gets. just be sure to safely stablize it. jackstands etc.
otherwise just follow the directions that come with them and youll love it.
i have one and i dont really see me going with any other exhaust. its ecerything i want.
nice and deep, but subtle.