DIY, change the tail light assembly on your Subaru Outback, the model produced between the years 2000 and 2004. This replacement is quite simple and it will only require a flat blade screwdriver and an 8 mm socket with a ratchet and extension. The whole process will probably not take you more than half an hour.
At the beginning, after you lift the back door of your car, you can go inside the trunk, behind the tail light you need to replace. Here you will have to remove two plastic covers, that should look like those in the image below. Use a flat blade screwdriver to pry them out and once you do it, you will gain access to the nuts that hold the assembly and the electrical harness that powers it.
So, the next step is to remove the nuts using an 8 mm socket wrench, with a ratchet and extension. You should be able to remove the one at the bottom quite easily. For the one at the top, the space is limited, so be careful not to drop the nut inside the body of the car, when you maneuver the socket wrench. After you do it, unplug the electrical harness powering the assembly and pull it out.
If you just need to service the light bulbs, you can simply twist their sockets counterclockwise and access them. There is no need to pull out the assembly and disconnect the main harness. You can service them after you remove the nuts and detach the tail light from the body of the car. If you need to replace the assembly, install the new one as the old one was, plug back the harness behind, secure it with the two nuts and reinstall the plastic covers. This is all you need to do, if you wish to remove and replace the tail light assembly on your Subaru Outback, the model made between the years 2000 and 2004.