[Christ]

1: Heat up the lights slightly, something like 150*-200* for 30 mins in the oven, but don't quote me on that, try it on a junk tail light first. After you heat them up, you should be able to wedge a wide, thin object (read: steak knife) between the lens and the housing, and gently pry up on it... This is how I get headlight lenses apart, even the plastic lenses. It doesn't fog them up or anything.. and I've put them in for up to an hour @ 200* to heat up the crap that seals it.

Before prying too far, check around the lens/housing for little clips. Once you've done the mod, you can re-seal the tail lights by cleaning off all the tar, and re-applying silicone sealant to the divot where the edge of the lens goes in the housing. (You'll see what I mean)

As far as the dual filament idea, I have no idea at 2am... check back later.