i cant seem to find that damn tutorial anywhere..all my galant websites have changed over to new programs and new servers in the last couple of years also and i think some stuff got lost, but anyway i do kinda of remember how to do it and got a couple of tips searching for it. so here goes.
DISCLAIMER: PERFORM AT OWN RISK. I DO NOT TAKE ANY RESPONSIBILTY IF YOU MESS UP YOUR STUFF.
NOTE: YOU WILL ONLY NEED TO DO THIS IF THE HEADLIGHT IS HELD TOGETHER WITH A RUBBERY ADHESIVE.
Before you start to take your lights apart, look around the edges to find any screws that hold the front and back together. Heat up your oven to 250 for about 10 minutes. SHUT OFF the oven and place the headlight in there for 7-10 minutes. Pull out your headlight and use a putty knife (or butter knife if the wife will let ya lol) and start seperating the clear cover from the back piece. Reheat in the oven as necessary. Now in the galant the reflector was just held in there by little grooves in each of the pieces so all you had to do was pry it out. As for the truck headlights you will have to figure that out when you get them apart. Putting them back together is just as easy. Put the clear piece back onto the back piece, attempting to use as much of the adhesive as possible if the light had screws put them back in as well. Re-heat your oven to 250 for 10 min, SHUT OFF OVEN and put the lights back in there. Remove after 5 minutes and spread the adhesive around the edges to help seal the lights back up. Now rather than putting your light back in the oven at the end you may decide you just want to use new silicone and i guess that would work as well.
Now as i was searching for this method i saw a lot of posts that recommended using a hair dryer or a heat gun. Unless you have some kind of jet engine hair dryer i think that would take way to long to heat up the adhesive that is used. If you dont want to use the oven method the heat gun seems to be like it would work the best, being that you are able to control the heat that you want.
Good luck and let us know if you try it and how it comes out.