Cracks can be welded as well, but anyhow, on to the Pro Circuit.
Normally, they are designed such that the pipe can be matched with a stock silencer, or a stock pipe with their silencer. Obviously, they also fit as a set. You should simply have to pop off your stock pipe, and bolt on the PC pipe. A quick jetting check to ensure it isn't lean isn't a bad idea, as pipes can alter jetting somewhat. the changes are normally small, and no jetting changes are required, but a few minute to check it is cheaper than losing an engine due to lean jetting.