Swapping Door Lock Cylinders

The driver's side door handle on my 81 380sl broke, but I managed to find a nice, used one. Can anyone tell me how to swap the cylinder
from my door handle -- which I imagine I can remove by turning the key -- with the one in the replacement, which doesn't have a key.
The only think I can think of is to remove the screw on the end of the replacement's spring loaded shaft. But I don't want to risk opening Pandora's box until I have some idea of what I'm doing.
Thanks very much in advance for any help anyone can give me.
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