Mercedes Benz repair: ignition key wont turn, mercedes 240d, w123

Question
when i tried to turn the 1981 mercedes 240d on the key in the ignition would not turn . it took about 10 minutes of wiggling it before i got it to work  then when i went to turn it off the engine kept on running even with the key out, i shift the gear and popped the clutch to turn it off.  now the key will not turn to turn it on at all. can you tell me what it could be and what part i need to replace? i purchased the car  just recently from an individual and he does not know what it is. thank you.  

Answer
I suggest taking it to the dealer, but the following should have all the answers you need.
http://garnet.acns.fsu.edu/~jjs5772/W123/

To turn off the engine, there is a lever on the injection pump, it says STOP, push it and engine will turn off.

Have a great day.