Somehow I was not surprised to read in the owner's manual that I needed to take my car in to the dealer simply to change a bulb. The owner's manual blames this on the fact that cars are becoming increasingly complex (which is of course their own fault).
I called my local Audi dealer and they quoted $80 (USD) to perform the repair service. Instead I went to the auto parts store and bought a replacement bulb set which contained two (P21/5W) bulbs for $3.97 (USD).
EASY DOES IT! WHILE STRAIGHTFORWARD, THIS PROCEDURE REQUIRES PATIENCE AND CARE. UNDERSTAND WHAT YOU ARE DOING BEFORE YOU DO IT. I AM NOT RESPONSIBLE FOR ANY DAMAGES CAUSED BY THE USE OR MISUSE OF THIS INFORMATION. PROCEED AT YOUR OWN RISK.
First I carefully opened the circular cover with a small flat head screw driver (it just pops out).
Then, using a Phillips head screw driver, I carefully loosened the screw that holds the entire light assembly in place. I knew I had the correct screw because as it got looser I was able to move the assembly slightly. While the screw might have been able to be recovered with a magnet if it had fallen in the body, I was careful to avoid this by only loosening it a bit at time.
Once the assembly was free of the screw, I gently pulled back the rubber material so that it was free of that rubber block.
Next I began to carefully pull the assembly away from the center of the car. In this case (because it's the left assembly) I began by pulling it gently to the left (not directly out because of the two plugs). I did this carefully as not to damage the plugs.
Once both plugs (top and bottom) were free of the body, the assembly was only connected by the wire.
Next I disconnected the socket from the assembly by carefully inserting a small flat head screw driver.
Finally I carefully separated the white piece from the assembly. The stop light bulb was the one at the bottom (it had two filaments). To remove it, I pressed down very gently and rotated it out counter-clockwise.
If you can' stand the thought of paying $100 just to have someone hook up a little cable underneath your dash to clear out a light, this is for you. We've all had that conversation... "Oh wow, you fixed it already? You just needed to erase the code, huh? Wait, how much? You're kidding. I saw what you did, I was standing right here the whole time, it took 10 minutes." THAT COSTS $100?!?!?!