the headers wont change how the car sounds much. the 97-03 Grand Prix have a "U-Bend" in the exhaust just before the converter and doesn't help the efficiency. a downpipe will fix that problem, but headers will help the engine breath a lot better. the only problem with the headers is that the downpipe hangs down a bit lower than what I am comfortable with, so I cut out the interlock flex section and welded in a shorter one. there are a lot of "how to" on this site, so welcome to the club.