My MX-900 is a few years old now and the select button is not working well. I have to push it very hard, usually multiple times, to get it to work. I thought I would just take it apart and clean the contacts inside but there are now screws! I simply don't see how this thing comes apart! It appears to be one solid piece of plastic, though I know it is not. Has anyone done this? Any tips? I don't want to break anything and if I can't get it apart I'll just bring it to work and let the tech do it.