Quote from gansodesoya:

why is step 3 necessary?

Just to disconnect any power source to avoid damages by short-circuits.

I think, that the needed Hex is actually a 1/16 inch Hex.

the 1.5mm works fine but seems to be a littlebit too small (But i can't test it since i do not own 1/16 inch Hex (but that one should be about 1.58mm).