The Apple iigs keyboard model A9M0330 key switch is comprised of several pieces. Three of which you can see on the outside and four you can see on the inside. Like the Apple iie key switch, the metal contacts fit inside slots which are located on the upper plastic piece. These are those contacts which when in contact together make a connection on the board where the switch is soldered onto. The key switch is a momentary push button single pole single throw normally open switch. The reasons for cleaning the switch are obvious. Simply pressing a key and you don't get the desired action on your screen. The pieces which can be seen on the outside are the upper black plastic piece, the lower black plastic piece and the white button piece. Inside the switch are the two metal contacts, a spring type of black plastic and a coil spring. All metal contacts inside the key switch must be clean and free of dirt and corrosion. One metal piece is a flat piece of metal bent in several ways while the other is what looks like a wire in a shape of a question mark. That piece should not be cleaned by a metal brush or with something harsh but instead should be burnished by a small flathead screwdriver. To remove the key switch from the keyboard, pry it up from the sides. To open the switch, look for the slots on the side of the switch and using a small screwdriver, move the piece of plastic there downwards as well as pushing it outwards at the same time. After doing one side, hold it with your fingers and do the other side. If you do not, then when you do the other side, the first side will close up. Once you have loosened both sides, use a small screwdriver to pry the sides open with a twisting motion. To reassemble the key switch, you must put into position all pieces that go into the top of the switch (the upper black plastic piece) before you close it up with the bottom black plastic piece. Each metal piece goes into a different slot on the top black plastic piece. These slots hold the metal pieces close enough together so that when the button is pushed, these metal pieces come together. The white plastic piece must be pushed down slightly (as if you were looking at it from above [top view]) the coil spring should sit on top of it and the spring type of black plastic piece should be installed on the other side relative to the metal contacts and pushed down so that it cannot be seen. Finally, install the bottom black plastic piece. After reassembly, if you find that pushing the button is much harder or impossible compared to the rest of the buttons, then you have made a mistake and you must try again after you check for any bends you might have made to the metal contacts inside the key switch. When installing the bottom black plastic piece, make sure that the contacts that are soldered into the board are pushed through the small holes on the bottom black plastic piece.
While I hope this guide is useful for anyone wishing to repair the Apple iigs keyboard, I assume no responsibility for any damage at all what-so-ever caused by anyone who decides to use this knowledge. If you shoot yourself in the head, then you pushed the trigger as much as you could not push that key on your messed up Apple iigs keyboard.
Sorry if I could not provide any pictures or videos of this process. However, if you are willing to send to me in the mail a very expensive $10,000.00 video camera, then I am willing to negotiate.