Help with 02 GT Convertible
 

I have bought my first mustang and would love some advice from the veterans. I do not want to go crazy at this time, but do want to add some more HP and sound. I will not have a problem with my dealership as to warranties, so that is not a issue. I would like to put on add on's with out having to experiment. Also, will someone explain for me about exhaust ( headers, H pipe & cats) Can this be one complete unit. Does the 02 have a factory header, do I need a aftermarket header and the difference with shorty and long headers.

Sorry for so many questions

Thanks in advance