[morzh]

I think you have all pieces in place, none broken. Get the gunk out, lube and re-assemble. It should click in place.
I think (I never dealt with this very one, only with similar ones), the round-cap-ended pin goes into the spring, and the ball goes between the shaft and this pin's cap.
The three balls in my shaft go into holes on the side and are propped up to the sides with the shaft that presses on them; this is a bit different, but the idea is, the balls are between the walls of the cylinder and the shaft and serve as a ball bearing, so there has to be some groove they go into.
The small ball and the spring keep the shaft taut. Usually, when assembled, the shaft is pushed in and clicks in place.

I do not know how this interacts with the pin; mine did not have it.
Also, see if you might find (Google it up) the info, Google your radio model and "tuning shaft assembly"; I am sure you are not the first person to deal with it. If not here than on ARF someone had to.