Do it yourself, change the tail light assembly on your Cadillac DeVille, the car model produced in the years 1994, 1995, 1996, 1997, 1998 and 1999. This repair needs a T15 torx scredriver and about 5 minutes of your time, because the replacement process is very, very simple.
There are two main steps until you can basically replace the tail light. First of all, you will have to remove a T15 torx screw on the upper side, as you can see in the picture below.
Now, the second step of the replacement is to pull out the tail light and detach the three light bulbs behind it (see image below). This can be done by twisting their sockets counterclockwise. The bulbs can now be serviced by simply pulling them out.
This is the moment when you can install the replacement tail light. You will have to reconnect the light bulbs and insert the assembly into the body of the car. You should do it by aligning it at the bottom first and then on the upper side, where you have that retainer. Secure the lens with the screw and that should be it. These are the simple steps you need to follow, if you plan to remove and replace by yourself the tail light on Cadilla DeVille, the model made between 1994 and 1999.