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The grinding noise from the headlight is indicative of a bad plastic gear inside the headlight motor. If you are reasonably handy you can rebuild the motor yourself. Easiest way is to purchase a repair kit that includes a new brass gear, bump stops, and everything you need. There are several on the market. I purchased one a few years ago from "carguy8t8" on eBay. Note: I believe there are two different types of headlight motors in a C5, depending on your year. One year (I think 2000) both styles were used, and you need to get the correct kit.