Bill01, here's what to do:
1. Clean the liner with automobile soap and water. Use a stiff brush and scrub the heck out of it. You'll be pleasantly surprised how good it will look at this point.
2. Use an "Armorall" type product on it. We prefer Just Once (
www.justonce.com) because it contains no oils or solvents.
3. You can take it to a LINE-X dealer and they can apply one of several products (Ultra Shield, Nason, or Xtra) that will permanently keep the liner black and shiny. Depending on what product you choose, price should be as low as $50.
HAPPY HOLIDAYS!
EDIT: If you do #3, don't do #2.