I dont know why the picture stopped working, ill try it again, if it still doesnt work right click on teh pciture and select show image. If it still doesnt work right click on it and select save target as.
The e-clip is the little retainer that holds the shaft in, its shaped like a C and clips onto the very back of the shaft (the oposite end that the prop is on)
I dont think its your shaft that messed up, its probobly just the center of the spur gear that is stripped out. The big gear is just pressed onto the shaft so it can be replaced later on if it gets messed up, the problem is with the gear being plastic and the shaft metal if you crash your plane with the motor still runing and the prop cant spin then the hole in the gear gets stripped.
By the way, our gearboxs are just about teh same except the shaft on mine isnt threaded, you have to use a seperate prop adapter. Other than that and the way they look they are like 99% the same.