actually if it is like what I am looking at you dont even have to remove the tumbler and lock and infamous black ring. If you look at the back side of switch *connector end* you'll see three small regular headed screws that hold the swich part onto the switch. Remove those three screws and the electrical assy should just pop off. Once off,, if your bold and brasin.. genly press in on the three small black tabs around the edge and remove the actual switch from the case. These switches are incredibly heavy built. You may be able to clean up the contacts and straighten them out a bit. If not.. ******** AZ has the new switch 1244620093 for about 30.00 including shipping.

http://www.***************/search/product.aspx?sid=yqbayxv3qr5sf245xhpkg3fp&makeid=800016@Mercedes&modelid=1194319@300TDT&year=1982&cid=25@Ignition%20Parts&gid=4520@Ignition%20Switch

Hope that helps you!

Rick