I am repairing a badly maimed Selectric Model 72.  Most of the mechanisms involved have been very easy to work with and replace.  However, I can't figure out how to remove busted keycaps or add my shiny new ones.  The usual suspects are involved here, the large "on-off" and "clr-set" keys.  Is there an "easy" way to pop them off so that I can swap out the parts?

Best to all of you -- Liam