I see... MB will always know the key regardless how old the car is...
Did you check the back of the ignition lock assembly? There is a switch back
there where there is a big plug of wires attached... if it is loose, then
try tightening the three screws if you can pull the plug off...
At this point, if your friend who has the spare lock assembly, is good
unit... turn the key and see if it feels normal... if yes, then put your new
tumbler into that one.
The key to get the old lock assembly out is that you need to get it to
position one... use a screwdriver into the hole with your tumbler out... and
try to get it into position one or so... it really doesn't matter as long it
is not in off/lock position...
Then you need to loosen the clamp by your steering column... and then you
need a straightened stiff cloth wire hanger,,, use the wire and fish it
through the front of dash to a detent... that will allow you to pull the
whole assembly out... the detent faces your seat and you should be able to
feel it with your finger.
Once the detent is pushed in, then you should be able to pull the whole lock
By the way, the lock assembly is $120 at the dealer.