I haven't seen any info on swapping out a Stinger lens, but there is a good thread on changing the lens on a Ultrastinger. You might get some good ideas from here:
They require a tool made by Streamlight to knock out the aluminum reflector from the outer piece, and to reinstall. My suggestion is one I did...Uniform companies, ones that supply police uniforms, found in most cities, may carry the tool as the cops use Streamlight. They let me use theirs for free as I bought the lens from them at the same time.