I know that installing headers can help a lot, but i have heard that the stock ones are good enough on the 2002 v6. Is this true, or would headers make a big difference?

 

The stock ones are pretty good on yours. If I were you, I would spend my elsewhere, and then come back to the headers. It is your car, so do as you wish. I'm sure you would notice a change in exhaust tone, as well as some extra horses.