A3-1.8T quattro - 4 wheel drive problems

Hi, being new to this I hope I've done this right! I recently purchased a 1.8T quattro, having had a full service including belts at my expense my audi specialist found it had been a bit neglected (although it has full history (not all Audi)). my question is there is a ticking from the back end around the diff', the ABS light comes on intermittantly and when the car is turning sharply, ie parking or doing a 'U' turn there is a loud clonk from the back end, I don't think my garage knows what the problem is as they won't give me a straight answer and I wondered if anyone could help and give me a rough price. Thanks Janey:1zhelp: