Mileage is not doable with vag-com unless its a brand new unit, and then it can be changed only once I believe, or possibly it can be rolled forward once. Mileage is stored in the ECU aswell. The immobiliser can be coded with vag-com but not without a login pin /skc.
information from the dead cluster can be done by removing the IC and reading it in a programmer if the not readable via
OBD, though with a login pin, you should just be able to code it in.
**edit**
http://wiki.ross-tech.com/wiki/index.php/Immobilizer#Immobilizer_Generation_3)