How do you change a bulb in the high level brake light of a 1999 Audi a3?

Answer 1

according to the book:

first take off the lower tailgate trim,

then take off the upper tailgate trim,

then you can take the high level brake light unit off by undoing a bolt and sliding it to one side.

Once it is off the bulbs just pull out apparently; they're 12v 2.3w

There may be short cuts to avoid taking the whole tailgate trim off; I'll find out when I try it myself in a few days time :-)

<time passes>

There's no shortcut, you have to take off both trims, but it wasn't really that hard.