DIY, change the tail light assembly on your Nissan Altima, the model manufactured in the years 1998, 1999, 2000 and 2001. This is a simple replacement process, that will require only an 8 mm socket wrench with a ratchet and extension and about 15 minutes of your time.
The whole process takes places in the trunk, where you need to move away the insulation behind the tail light, first. You can do it after you remove the thumb screw shown in the picture below. It simply twists counterclockwise.
By pulling away that insulation, you will gain access behind the tail light assembly you need to replace. If you just need to service the light bulbs, you can do it very simply now, by hand. If you look to replace the tail light lens, unplug the connector seen in the next image and then move to the nuts that hold the assembly.
There are four of them and can be removed with an 8 mm socket with a ratchet and extension (see details in the images below). After you get rid of them, the tail light will come out easily.
Install the new tail light into the body of the car, secure it with the nuts, plug back its electrical harness and put the insulation back. This is all you need to do, if you wish to remove and replace the tail light assembly on your Nissan Altima, the model made between the years 1998 and 2001.