1) I totally broke the existing tail light in place after having purchased a replacement from eBay seller, [email protected] (blatant plug) for $100. It arrived brand new with all bulbs in place. WOW! Money well spent.
2) Start by removing the screws securing the rear bumper to the fender well (5 Torx screws).
3) Yank the bumper loose from the clips that hold it in place all the way across to the middle. You'll need to do this for access to the tail light securing devices. You don't need to be very gentle as you will have to pound it to get it back in place.
4) Once the "guts" behind the bumper are exposed, remove the two hollow form modules by unscrewing them from the exposed inside body. You will have to bend the bumper back by hand (a second person would be really handy for this) to expose the screws (4 8mm) that secure these form modules to the underside. They supply a solid surface for the bumper to rest.
5) Inside the trunk, there is a panel that conceals the back of the tail light. Remove it by hand.
NOTE: The panel that covers full access to the tail light assembly in the trunk can not be removed for further access. I decided to cut the panel at the point where the trunk hinge passes through the panel to allow me to bend it out from covering the tail light. I also had to remove two nuts that hold the panel to the floor of the car. Not pretty as it leaves the panel somewhat unsecured, but, I saw no other way.
6) Remove the two plugs that connect to the car's electrical system. One is keyed, a securing latch has to be depressed, while the other can be removed by wiggling back and forth (hard to remove).
7) Press the two "wings" that hold the bulb holder to the tail light assembly and set aside (gently).
Unscrew the three 8mm screws that hold the tail light assembly to the car.9) In the exposed inside of the bumper, remove the screw, 8mm, that secures the tail light assembly to the body. It's located at the end of the tail light that tapers down to a point leading to the front of the car.
10) Remove the existing tail light assembly by pulling it straight out. There are two retention clips on the inside of the trunk that have to be pressed to allow the assembly to be removed. (That second person would be very handy at this point).
11) Replacement is the reversal of these steps. Pay extra attention to the assembly seating securely in the rear compartment where the original assembly came from.
SUCCESS! Reward yourself with a beer or other adult beverage and exult at your mechanical genius. Ya' know, it's funny that Volvo designed a headlight module that is released by pulling out two "pins" under the hood, but, they make one go through disassembling half the car to replace a tail light assembly. Shame On Them!
PS. I test my back lights by backing up to a business or other building that has a plate glass window. Make sure that all of the bulb illuminate, backup, brake, parking, and emergency.