C220 CDI 1999-FUEL PUMP DRIVE PROBLEM
 

My C Class 220 cdi is '99 on a "v" and recenly stopped while out driving-after being towed to local independent Merc specialist they have advised me that the drive/cog that is attached to fuel pump from engine has collapsed/worn and needs replaced, which is reason why car will not start, - part apparently only costs £41.00 plus vat but problem is that garage has said they may have to take the cylinder head off to change this part!!! Is this correct? Is there any way round it?
IF ANY ONE CAN HELP WITH ADVICE TO AVOID REMOVING CYLINDER HEAD WOULD BE MOST APPRECIATED OR EXPERIENCED SIMILIAR PROBLEMS AND CAN OFFER AN ALTERNATIVE I WILL BE VERY GRATEFUL