I actually went by a Mercedes Parts department yesturday and inquired about a replacement key.
I was informed that I am locked in to Chrysler because all keys are based on the VIN numbers and that changing from that worthless fob, in which key ring breaks off, to a key was not possible.
He also informed me that the shell were not also not available and that both Chrysler and Mercedes have changed their design because of this.
I rented a Mitubitshi which had designed their key fob to withstand a hard throw against a wall.
At present I am contamplating buying a key for $100 plus and knowing that that the key ring will fall off if knocked off a end table on carpet.