I had to ues a different key for the ignition on my 84 300D, so after reading some threads, I went to the local MB dealer and ordered a new tumbler and key that matches my VIN. The tumbler arrived today, and thanks to those who offered advice on how to remove the old one and replace with the new one, I had the whole thing done in less than 10 minutes. The only tool I used was a large paper clip. The cost of the new tumbler was $58.00, including tax!
Thanks guys for your advice. It's nice to only use one key for the ignition and all the locks.!