You can clean the lenses pretty easily. There are some products on the net for cleaning plastic head lights.
Other methods include wetsanding the lense with 1200 grit wet sandpaper using WD-40 for the "wet" as a lubricant. This will bring them right back to their original luster.
http://www.autogeek.net/plastik-lens-cleaner.html
http://www.superiorcarcare.net/plastik-lens-cleaning.html
http://www.autopia-carcare.com/meg-g-12310.html
Regards,