You can literally unplug and plug in cables and slot in parts. That is all there is to disassembling and assembling a keyboard. The catch is that you have to know where everything goes. You can easily learn how to do that by watching YouTube videos. There are many comprehensive videos there.
If you are making the first disassembly or repair, you need to pay attention to basic safety precautions.
1. Please ensure that device is disconnected from the different sources of power such as battery or power supply adapter.
2. Remove all rings, bracelets, watches and any other metal objects from your hands.
3. Strongly recommended use a ground strap on your hand or antistatic gloves to protect the unit from static discharge.