Final update: I was not entirely happy with the sound. It was clearer than before, but not as good as I would like. So I took up aspergerguy's kind offer and swapped the earpiece. As I am sure you are all keen to hear, the operation was successful, the patient is... alive!

The only casualty was one T5 screw. I managed to damage the head, so the screwdriver does not grip it any more. I did not think T5 screws could be stripped like that, but apparently yours truly is capable of the impossible.