Replacing a bad key switch on an Apple Extended Keyboard

I've used and loved my Apple Extended Keyboard (I) since 1989, but in moving it to a new office, the right arrow key has stopped working reliably. It requires a ton of force applied for several seconds for the key press to be registered. Taking off the key cap of the right and left arrow, and listening closely, the right arrow key switch sounds very mushy compared to the left arrow key switch. I figure it's just finally gone bad. What I don't know is how to fix or replace it, or if it's even possible. Anyone done it before?