Now I know
A couple of months ago the ignition in my 91 190e started getting unfriendly. Most cars work the same way, the key needs to be turned to get the guts out so I was already getting nervious. Surfing here I found Mercedes is especially expensive if you pass the point of no return so I bit the bullet and ordered one from the dealer and sweated till it came in. It only took a day of two to get it so I don't know why yours is taking so long. While it was acting up I found a technique that always got it out: while appling slight pressure turning the key quickly jiggle the key in and out. Oiling it helps too. Once I got it out looking at the mechanism I came up with a theory on getting a stuck one out. There is a shell, or cover that surrounds the mechanism with two slots that align with two holes in the tumbler when the key is turned that you stick wires in to release the lock. If you can predict where those holes are, like by looking at the new part, and put holes in the cover so you can stick the wire in it might unlock it. You've got nothing to loose trying it, its all going to get destroyed anyway.
I was wondering if you had any warning about it dying. And as I said, now I know how much I saved.