These sound like two separate problems. Solving either or both of them will require removing the motor from the frame, and splitting the cases. You should start by buying a service manual for your model of bike, and reviewing the procedure, in order to decide whether you want to tackle it yourself.
The kick-starter problem is probably just a matter of replacing the spring inside the right engine case. The transmission issue is likely a damaged shifter fork, but the only way to be certain is to inspect the parts. It is also possible that the kick-start spring broke, and the broken-off piece has fouled the transmission. This is quite a large job, and you will need to decide whether it is worth the effort on a 39 year old machine.
