The stuff that holds the lens to the base does NOT react to heat. It is a cured glue, not melted goo. The lens is VERY sensative to heat and the protective coating will crack (spiderweb) with a heatgun near it.
The ONLY safe way to get the headlight apart is by cutting it. If you are looking for an easier way to get it apart, you're just going to find an easy way to need a new headlight.
