I need to know how to make my 87 420SEL trunk lock work or how to replace it.

1. I can lock and unlock my trunk by using my central locking system, i.e. by locking and unlocking one of the front doors.
2. When I tried to use the key in the trunk lock it doesn’t work. I can turn it very little clockwise and back but it doesn’t turn anticlockwise at all.
3. Doing that it doesn’t activate the central locking system.
4. I have another 420SEL I’m using for parts and its trunk lock works fine.

I need help to either:

1. Fix my lock.
2. Replace it with the one from the parts car
3. If I replace it, how can I make the door key work in the replaced trunk look?
4. I tried to remove the lock by removing the screw in the top and the nuts inside the trunk but it didn’t work it looks like there is something else holding it.

I appreciate your help doing that as I’m afraid not to be able to unlock my trunk if the central locking system stops working for any reason.

I did it already. Thanks