Rule NO. 1 buy yourself a set of precision screwdrivers when you're dealing with Tamagotchis. I always use the one you see pictured above. I use a set of six screwdrivers from 1.4mm - 3.0mm. It comes in so handy dandy when you need to replace the batteries. The older Tamagotchis use two LR44 batteries and the Arukotchi and Connection need a CR2032 battery.
This is our testmodel. Oh what a luck, it is dead already ;-) First whe have to unscrew the tiny screws on the back. Now you can replace your batteries, both with a plus (+) upwards. Notice the 4 small screw here? lets unscrew these too.
Lets see what whe've got here... 4 larger screws (one got stuck as you might notice) The green thing is the circuit board where all the action comes from. The yellow circle is where the sound comes from. The grey button on the left is the reset button. Lets lift up the circuit board now...
Oh look, it's the screen that's attached to the circuit board. The colours on the screen come from a little piece of paper behind the screen. You can actually redesign it, read more about it here. The front of the tamagotchi has got a plastic clear sreen and buttons on the bottom. You could change the buttons with another Tamagotchi if you would like to create your own unique colour combination.
Well that's it, this critter has been put back together again ^_^