BMW Repair: setting mileage on odometer, audasity, bmw 325

Question
I have a 1984 BMW 325-e.  I have to replace the speedometer head on my car.  I am going to buy a used part and have a repair shop install the "new" speedo head.  Neither the used parts dealer nor the repair shop know how to reset the mileage on the odometer.  How do I set the mileage?

The old speedometer has the following number below the current mileage:

k=7849eg

Any help would be greatly appreciated.

Answer
the only way i know of risks perminant damage to the unit.  BMW's were designed so you cannot easly turn forward or back the odometer.  
should you have the audasity:
take the plastic cover off the rear of the unit
remove the top most circuit board untill you can get a screwdriver or paperclip to spin the numbers manualy, they move more easly forward then they do backwards.
-cheers