it is possible but not very easily done and usually costs (from what I've heard) quite a bit of money. Plus, sending it away still means you can't drive the car while its out. I don't think they would care (or use) the extra buttons. They are only for volts and trans temp and oil life and such and fuel economy. The actual mileage shows up as soon as you open the door or push the trip button and that still works no matter the buttons that are connected. I'm thinking mostly for inspections when they check the miles. Even though for warantee work, the shop could look at either the BCM or the DIC to see what they are... if they match, I don't think they'd care what buttons work and what don't.
