Walk behind Replacing self propel compression springs Toro 20065

Greetings: I'm trying to replace the tiny "compression spring" on each side of the self propel transmission shaft of a Toro model 20065. Anybody have an easy (or not so difficult) way of doing that? I know the key is supposed to fit over the spring prior to placing the gear over spring/key on the shaft but how do you keep the key from flying off? Thanks in advance.

Put spring in place then put the key on spring. Push key into the slot and use pliers to hold the key down. Then slide bearings over the key.