The manual makes it look easy. It's a fiddly ballache to work round the security plate that's over the handle.
2 screws security cover.
2 screws plate and handle.
Control rod to lock there's a spring clip holding holding the plastic end of the rod into the back of the barrel and the centre pulls out.
The control rod to handle you can push (with difficulty) the pivot pin past the plastic barb in the lever at the back of the handle. (Maybe makes more sense when you actually look at it.
Put some masking around the outside of the door handle. I recall a lot of 'chewing about' with not much room to maneuvre, inside and outside the door.

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Search door handles there is loads of "How To" fix this common fault.