Controller configuration was really easy. The kit I ordered had the buttons, joystick and the usb adapter. Each button has fork connectors for the button side and a plastic connector for the usb adapter side. Joystick has a 5 pin molex connector. Then I used the controller configuration in RetroPie to setup the actual button mappings. The one/two player buttons on the front are LED buttons, but I disconnected the LED portion as they were pretty bright and distracting. For power, I used a momentary push button and the info from this youtube video: https://www.youtube.com/watch?v=sh17hT0SCq0&t=51s.
I also used a relay connected to the Raspberry Pi to control the marquee LED power, as I wanted it to turn on and off automatically.
It might look that way, but there was a good amount of trial and error involved. Good news is that I didn't make any major enough mistakes to have to restart the whole project, just a few boards here and there.