To take them apart, just unscrew 4 screw and take the top off. Then you can take the ball out and clean it with whatever you like. Each of the roller can also come up by lifting it, clean those and if not badly used they will make the ball roll smoothly.
For additional mounting help, look down a bunch of post and there should be one discussing the varies mounting options. Both Happ and Betson mount about the same ways.
BTW, if you want to go cheap, you could also hack a mouse to interface with it. It's not as great as the opti-wiz, but it's still very decent. I have had very good luck with the 2 button plus scroll ps2 intelimouse with ball. Optical mouse won't work.