I do headlight mods as a hobby, so Ill try to help as much as I can.
Take the lamp off the truck. Take all the bulbs and wires off of it. I forget if the Taco lamp has screws or not, but go around the perimeter and if there are any screws, remove them.
Take everything out of the oven, put a rack ont he lowest possible setting, put a baking sheet on it. Preheat to 250*.
Put the lamp in, 1 at a time, for 6 minutes. Pull it out, start in a corner, use a flathead if needed, and pull it apart. If its giving you a hard time, put it back in for 2 minutes at a time.
Once its apart, remove what you need to (I think there are 2 amber reflectors).
To reassemble the lamp, putt he BACK portion of the lamp in the oven for 3 minutes, pull it out, put the lens on, and push it together. Reinstall the screws if needed. If it isnt holding itself together, you might need some clamps to hold it while the sealant hardens back up.
Odd question here, but if my corners are leaking water into them, is there any chance you could reseal them in this method? I couldnt care less about some amber in there, I just dont like seeing them full of water/condensation.