The process is actually quite simple, and can be accomplished by anyone with minimal mechanical skills turning a wrench. However, there are a couple of tasks which most likely an owner will have to go to the dealer -- programming the center console control unit for example.
Also note that the parts required and a few work procedures will be different for 991 Base (3.4L) cars vs. the S 3.8L variants. This is due to different side exhaust units found between the two.
Anyways -- here is a copy of the instructions. Feel free to contact me if you have any questions or require additional manuals.