Just done mine on a 66 plate A4 Avant - £88 from Audi. Kinda wish I got one off eBay for a tenner…
Fingers crossed ABS is still ok - my warning message disappeared after it first appeared so assumed all was ok and carried on driving until it came back on a few weeks later. Then I stopped driving it immediately and replaced the sensor, having found this thread.
Really not impressed with my Audi - great car when it works but there always seems to be something wrong with it! Last car was a Peugeot 308 and nothing ever went wrong in over over 100k miles/10 years…
Please note that the sensor does not just pull out vertically - there are two clips that need to be released, which is quite a fiddle as it’s dark and a bit restricted access plus I found the wire a bit tricky to remove. Defo recommend watching the video BEFORE attempting it!