a4 avant 2005 TDI goes in for grinding 3rd gear and has gear box out and repaired, new clutch and fly wheel. All put together and garage says car wont start. gear box off and on again to check something or other, checked diagnostics and changed a range of sensors, now saying it is cam position sensor and need to remove cam belt to get at it. And they want me to pay for cam belt job. I have completely lost confidence in this garage. what have they done to my car.. how can it go in working, have a gear box on and off and now need a new cam position sensor..?