Pic 1. When installing the dial into the face piece, hold dial so that the ball is facing up, and turn the face untill one of the 2 V grooves lines up, it goes in easy then.
Pic 2. Spring/gear assembly, spring, and dial/face assemble. Center spring goes in one way, one end fits tightly around the spring/gear assembly, the other end is larger and goes around the tabs sticking out of the back of the dial face.
Pic 3. Press together and twist to assemble. The tabs on the gear/spring go into the grooves of the dial. But you were watching when you took it apart right?