That's right, never ever buy a Chrysler part if possible, always buy the Mercedes part. The Mercedes part number canbe found on most parts unless the part is an over the counter commonly used part.
You will need to match the tumblers on the insert so that it matches your key, otherwise you will need two keys, one for the ignition and one for the drivers door,. You would be in deep trouble if the door did not open using the fob, you would be locked out. Any key part that came with the ignition insert should match the fob attachment, the one shown above does not look like the part at all.