If you have ever purchased and assembled a model you will discover quickly that there are no step by step instructions.  It is best to concentrate on specific areas of the model and create sub-assemblies that can then be assembled into a complete model.  The following are the sub-assemblies.

Print and assemble one switch.  When you are satisfied, repeat the steps 18 more times.  

Print the rest of the 3D parts.  Install inserts.  This was fairly straight forward.  Verify fit as you print each part.

I first wrote the protocol between the Arduinos and Raspberry Pi.  I then wrote the code for the Arduinos.  Finally I wrote the code for the Raspberry Pi. The Raspberry Pi needs to be set up to be able to remotely access and control once the back cover is closed up.

Install the switches and then solder the diodes and wires to make the keyboard, routing the wires to the Arduino assigned to the keyboard and test.

Install the processors and if wiring the AGC connector, connect it now.

Assemble all the sub-systems.

Install the software and enable them as services.  Test the software.