Anthony, don't know for sure, but go to
www.colorplus.com. The owner of those products is great. Her name is Joanne. She might have a leather dye system that could help you accomplish part of your task. Give her a call or send her an e-mail. She is very responsive and was a recent "door prize" sponsor for our early May
Tail of the Dragon Trip.
Maybe you can pull off the leather covers on the seats and replace with black. A good leather shop could make these for you. Or buy from Porsche...but that would be $$$. New seats, like the GT3 seat.....$$$...again.
Other leather trim pieces...take off...and re-cover with black leather...could be a DIY project.