1Get the PCB made
Eagle files attached to this project. I used PCBGogo to make mine.
Clone the repo, open in Arduino. Straight-forward stuff.
I tried to label all the parts on the PCB and everything lines up so it should be pretty easy.
If you're having trouble soldering the pins on the flex connectors, get a better iron! I upgraded to a fx-888 and my soldering time for the board went from 1 hour to about 15 mins.