Removing the lens from the housing is easier than it seems. The hardest part is actually getting the housings out of the car.
Start by removing the metal clips, use a screwdriver. Next, start applying heat with your heat gun on the wide end, working your way to the narrow end. DO NOT pry with a screwdriver or any other hard object. The housings are made of soft plastic, and you will damage them when they are warm.
As you heat the lens, the adhesive will get soft. Start trying to pry (GENTLY!!!) from the wide end. You might want to ware some gloves, they will be pretty warm. As you pry, you will expose some adhesive, give it a little more heat to speed the process along.
At the narrow end, the lens actually slips into the housing, so don't pry it all the way off. You will need to heat the narrow end, and lift it out of the groove.
To remove the amber reflector, use a pair of wire cutters, or some other type of cutter to clip off the little tabs. The reflector will just fall out. Take this time to carefully clean the inside of the lens. Careful, the chrome is very very thin..