central door locking bother

[tonymcb]

hi about to purchase a 1997 A4 TDI estate off my cousin he has told me that the central door locking doesn,t work also the diesel flap doesn,t open and the tailgate. I am confident I can fix this with your help .apperently the box of tricks in the rear of the boot is broken the ceramic disk that spins is broken sattered into 4 pieces is it posible to fix or is it a new one needed have looked in loads of scap yards but it must be a common fault as they are like hens teeth to find cause they have already been taken. how much is a new one from Audi