DIY, change the tail light assembly on your Saab 9-3, the model produced from the year 2002 until 2014, when the car manufacturer stopped producing it. You will require a flat blade screwdriver and a 10 mm wrench, or a socket of the same size. The whole process will not take you more than 20 minutes.
The repair starts in your trunk. Open it and grab on the plastic button seen in the picture below and pull out a trim panel that covers the back of the tail light assembly.
So, once you remove that panel, you will get access to the tail light bulbs and electrical wires behind the assembly. Push up the plastic tab seen in the next image and pull out a plate containing the three light bulbs. Replace them if needed or move further, to remove the tail light.
In order to do it, you will have to remove the three 10 mm nuts that hold it (see the top one on the next picture). You can do it with a wrench, or a socket with a ratchet.
Pull out the old assembly, install the new one, secure it with the nuts, reinstall the light bulb plate and cover everything with the trim panel. This is all you need to, if you wish to remove and replace by yourself, the tail light assembly on Saab 9-3, the model manufactured between the years 2002 and 2014.