You can do the insides if you want. What you have to do is put the headlight assembly in an oven that is cold and ramp it up to 400 deg. Once it hits 400, or about 5 minutes, remove the headlamp assembly and pull it apart. Be very careful when pulling apart so as not to break either the lense, or the housing itself. I have done this several times.
Once you have buffed out the inside, and removed the most likely burnt reflector, you can put them back together. What I did was use the black windshield glue to hold them together. Not only will it glue them, but will make them waterproof as well. :Beer