All our cars have that problem, don't worry! I have removed all the tiny scratches on mine last week by using Meguiar's PlastX. It works great, and doesn't cost very much (10$ CDN at Canadian Tire).
I was able to get glass-smooth lenses, yellowing is gone too. I was at my parent's house when I did this, and we also fixed their Grand Am's where the block heater plug had scratched the headlight lens. The large scratch disappeared completely, leaving a perfectly clear lens.
Having a Contour, you also have the option of buying new assemblies, they are available for your car - I don't have that option with the Mystique!
