Electrical problem
1999 Dodge Ram V8 Two Wheel Drive Automatic 103K miles

All of a sudden my amp meter showed that my battery was not charging. I took my vehicle to the repair shop and they changed the alternator, however almost immediately after that, it began to show not charging again. I took it back to the shop and they informed that the Ignition Control Module had a short in it, which wouldn't allow my battery to be charged since it alternator was connected to it. They changed the ICM and so far it appears to be charging again, however the ABS and break lights come on after the vehicle is started and you begin driving. They informed me that it's because the VIN number for the vehicle doesn't match exactly to the ICM (which they installed used) and that it would have to be changed at the dealer. Does this sound like a valid answer and can the dealer modify the VIN in the ICM?