Sad event, if you had just got a used cluster and reset the odometer to the 66k all would have been well. This ideal of the cars resale dropping to half is insane. If you must install the new cluster with zero showing at least have a legal document prepared describing the whole event and have it notorized with all pertinate documentation attached. In reality the milage is known. A phone call to the mercedes zone office just might get your problem resolved as well. Nothing ventured nothing gained type of thing. If and when your old cluster shows up make absolutly certain all this is corrected.