Its not to bad a job, I rebuilt one by trial and error and it works fine, I took off the recirculation tube, held the nut on the centre of the the screw, as best I could, and then feed the balls back down the pick up shaft, I did it from one side and used plenty of oil so I could keep pushing them (and rotating the screw) until they appeared at the other side, (That way there are no gaps). Refit the recirulation tube job done...

I tryed other ways but its easy to jam the whole thing up so take your time :o)