Hi,
unfortunately I think it is almost worthless. The 996 is seriously cheap to buy now, and the part prices follow. And, many replace the stock exhaust for something else, giving the very few looking for an exhaust plenty to choose from. It looks nice but I believe it is made from stainless steel, hence looking food. It is definately not brand new. You can see that from the soot and discoloration.
The easiest way is to follow an ebay auction, like this one:
2000 2004 Porsche 996 Exhaust System Complete | eBay
I would guess she can get $500 for it, with the right buyer maybe a bit more, but it could take a while.
Regards,
Johan