Many members here have asked about how to cope with the age related clouding of polycarbonate headlight lenses by constant exposure to UV rays. Most of this damage is surface level and can be corrected by using a kit that using several steps to take away the clouded layer and then Polish the surface back to transparent. One good kit with which I have "hands on" experience with, can be found at GM dealers. The GM number is Part# 875428-1 Headlamp Restoration Kit. This kits sells on average for $ 28.90 + tax. Its a 3 step process, complete with directions, and everything needed to do the job more than once included. This is a quality product and I have seen the results for myself.
More information at Kwik-N-Klear.com