After looking at the Priefert web site it looks like they use the same gearboxes as the Tarter units. If I was going to do all that re-working on the KK unit I would probably set it up to change it to a reverse unit. If you are using the tillers on real hard pan surface then maybe a reverse unit would help more it you do not have rocks to deal with.
thats a thought; so after replacing the gearbox, do I just reverse the tines? As far as the work involved to repair it; minimal. Looking at it I am surprised the metal is so thin and feel this is why KK look bad so early. When I do the repair i'll post pictures to show what I found..