I just ran into the same thing with my spare Audi TT key fob, found this thread but no video. So here's what I did and was a snap to do
Case separation is easy by simply placing the tip of a flat screwdriver or butter knife in the indent on the side that has the Audi symbol and turning it to apply pressure pushing the two halves apart. One half is the mechanical switchblade key and the other, with the buttons, is the electronic half.
The electronic side with the FCC and ID numbers on it DOES pry open. The entire top will come off, not just the small square with the writing on it and the Figure 8 key ring will fall loose. Remember to put it back when clicking the case back together.
When you pop that part off, you'll see the two little batteries stacked on top of one another, both positive side down.
Hope that helps!
Ron