Thanks for the info. Getting a new ignition cylinder and new master key from the dealer sounds relatively affordable and easy to swap out.

Oh, and for the record. I bought a new master key for my 300D sedan within the last year from the Mercedes Classic center in Irvine, so I know you can still get the keys from them if you can provide them with the VIN number. Not sure they still provide the ignition cylinder but I'm going to reach out to them and hopefully they can still help with that. Thanks!