Before you spend a ton of money try the following.....
Get out your bottle of insect repellent (OFF Deep Woods is my favorite) and a paper towel. Spray a liberal amount on the towel and wet the headlight lens thoroughly, being careful not to get it on your paint. Rub the lens with the wet towel until the yellow haze is removed. You may need to follow up with additional spray on stubborn spots, but the result is AMAZING!!!