Take a look at this instructional video and learn how to take apart a Casio fx-82MS calculator. First, you'll need to get a screwdriver the take off the calculator's backplate. Make sure not to misplace those screws afterwards. You should be able to see the motherchip after taking off the plate, this is the next item you'll want to remove. These screws are extremely small so it might be best to use a knife to unscrew them. Lift the motherchip and take out the rubber key pad off. To put it back together, simply reverse this process.