I just replaced mine last week. Its relatively easy, except for that upper screw!!
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Get a set of jewelers screwdrivers at Lowes or Home Depot, or cut off a small (really small) screwdriver and you'll be fine. It took about half an hour start to finish. My symptoms were not being able to remove the key, the alarm wouldn't work, remote wouldn't work most of the time, and a few other little issues. The Audi part was less than $40. I was afraid they wouldn't have it in stock, silly me! The parts guy said I was the second or third one that day looking for that part. He didn't even need to look it up in the computer
Bob