REALLY straightforward :)
Have a plate or other clean, plain surface - as you unscrew them just lay out the scerws in their physical order and positions on the plate.
I DIDN'T disconnect the battery, but was VERY careful not to touch ANYTHING other than the disk - I guess that's feasibly where an accident might happen.
Go slow, keep touching a metal radiator or similar to ensure there is no static build up, and... DONE! Thanks iFixit :)