Bummer!!
Never done one but preload is crucial to long life, I have done preloads before on things with FISHING SCALES, and measured levers so ratio was same etc.
Just find out what preload should be and DIY, not hard just a bit of an arse to do under car.
I'll look into this for you but will take a few days.
I would not let your neighbour do any more(damage)!!
tabetha