any thoughts or ideas on where to go or what to buy to restore "vanilla" colored leather seats.

Find a local upholstery shop and ask. The seats can be re-colored. I had this done on the front seats in my 1995 S6 with the Beige interior and they looked infinitely better. The work is usually done by a jobber who travels from shop to shop. They clean and lightly sand the seats, mask the interior of the car and spray the seats with leather dye. You want to get references and make sure the guy has a reputation for meticulous work. You don't want overspray all over your interior.