Yep. Possible. Cost, depends on what you think is reasonable.
+1. Gunga has a good rep for upgrades.
If you're a DIY'er, as with mods to most such tightly built lights, the most challenging part is getting at the emitter. For the Preon a straight emitter swap for better tint, even with no driver tweaking does wonders. Either Nichia 219b or 219c will fit/reflow directly onto the original MCPCB. I have a 219b in mine and love it.
The pill doesn't want to come out so it needs to be coaxed. I did mine by working off the glued driver/circuit board from the end of the pill, so that I could unscrew the rest of pill itself. The tricky part about this approach is that the wires remain attached until the pill can be extracted. If you've never performed such surgery on a light before, sending it out to someone who has already paid their dues to the mod-gods (through hard knocks) is always a safe option.
Good luck.
oo:
