Usually the inside of your headlights dont get dirty it is basically a closed system. It maybe the outside of the lights. Try using Maguires plastx on the outside. It clearsup plastic really well. If you do want to take them apart, this might sound crazy but it is basically the easiest way, you will want to heat up your oven to 300* then turn it off when it is at 300 degrees. (THIS IS IMPORTANT BECAUSE YOU DON'T WANT TO COOK YOUR HEADLIGHTS) Put them inside for about 10-15 min. Then take them out and pry them apart from sides. You might have to reheat several time before getting them apart. If you take them apart you should paint the housing. If you have any questions private message me.