I have never taken a keyboard apart yet, and
will no doubt need to someday. I probably won't
bother until a keyboard, or keys, starts failing.
Start with a PC keyboard, and just yank the keytops off.
EXCEPT THE SPACE BAR!! Leave it alone until you know what you are doing.
IIRC, for the IBM 'clocky' keyboards, IBM would supply any keytop as a
spare (or maybe a set of keytops was a single part number) _apart from
the space bar_ which was not considered field-replacable. Having taken an
oroignal PC keyboard totally apert (and reassembled it!), I can see why.
Most of the keycaps just pull off and clip back on, but to do the space
bar you ahve to remove all teh otehr keytops first, then remove the back
plate/PCB, take out all the 'flaps' and then you can work on the spacebar
linkage.
-tony