how to repair yellowed headlights

Another thing to make note of, depending how "yellow" and oxidized your lights are, you might not need to start with such an abrasive grit. If they're just turning yellow and not really pitted from road debris, or severely sun damaged, feel free to start with 500 or so. Something else that really clears off the yellow is a rag full of paint thinner after the initial rough sanding. Just keep in mind you'll definitely have to go over them with sand paper in different stages to polish them after that, since it turns them cloudy almost instantly.

And don’t have the rag on there too long, it actually will start breaking down the plastic. Just enough to get the initial junk off the lens, then wash it off in cold water and start with the sanding.