First, start by removing the tail lights from the car. You need to twist each bulb out of its socket in the light housing (there are two sockets on the outboard lights, three on the inboard lights). Then, using an 8mm wrench or ratchet, unbolt the top and bottom nut holding the stud in place. The light housings are likely stuck to the paint in the buckets; you may need some force to get them out, and paint may come off. Don't worry though, it will be covered up by the lights when you reinstall them.
After the lights are out, prepare yourself for 3 or 4 hours of arts and crafts with plastic shreds going everywhere. Getting the lens separated from the housing took me a full hour on my first attempt, and I got the process down to 15 minutes by my fourth attempt.
The first step is to cut out the black glue that holds the lenses to the housings. I did this using a rotary tool with a diamond cutoff wheel. Basically, go deep enough until you hit real resistance, then you know you bottomed out the glue. Now using that depth, go around the entire circumference.
After the glue is cut out, there will be a touch more that you can't get to on the vertical portion of the housing/lens junction. You need to take a prying instrument (I used a flat bladed scraper) to pry the plastic lens off of the housing, do it every 1/2" all the way around the circumference.
Soon, you will be able to get a side pried up a bit; once this happens, go to the other side and try to pry that up. Keep going until you can finally lift the lens off of the housing.
Next, you need to cut the clear plastic diffuser disk out of the light housing. Using your rotary tool, cut from the center out at an angle all the way around the circumference, being careful not to knick the lens when you cut through the diffuser. This will not free it, but is necessary for the next cut, which will be from the outside angled inward. After you complete this cut, the disk should be free.
Now you have a mess! And a red lens, a chrome housing, a conical light shield for the reverse lamp, and a clear diffuser disk with a jagged center hole. Not to worry though, we will clean things up and hide the ugly bits later. At this point, the conical light shield and the clear or yellow glass lens for it can be archived or thrown away as these will not be used in upgraded lights.