Your best bet it to buy a Macintosh Plus keyboard, plentiful and cheap. It's the same keyswitch and gives you a backup of spares. Those old plastic stalks are going to start breaking as they get older and more brittle under the stress of use. Get yourself a copy of Larry Pina's Macintosh Repair

and Upgrade Secrets. Not sure if Tom Lee's tutorial covers that or not. http://68kmla.org/files/classicmac2.pdf