I did all that work and kept detailed notes. All the notes went with the machine when I sold it in December.
However, I don't know that I would use the same components I did then.
I would start with a G540 Gecko, because it makes everything simpler and more importantly, you can draw on the tech support from Gecko as well as the vast numbers of people of have used it.
Next is the spindle drive board. It's a KB Electronics stock part. Docs on the KB Electronics website.
I think you can connect it as-is, but KB makes a board that snaps over it and makes connections dead simple. It accepts the 0-10V standard spindle drive signal from any breakout board. To get it going you can just use a simple potentiometer to control spindle speed.
Beyond that you need a power supply, I used a 24V 10A to be conservative, as I did not have any specs on the stepper motors except that the drives are max 2A.
I would recommend 3 new steppers with known specs, and a power supply to match.
Alternately, look at Acorn. Acorn CNC controller, Step and Direction 4 axis CNC Control board with ethernet communication.DIY CNC kit
You get an all-in-one main board, plus very good software (equivalent to Mach3/4, perhaps better), plus PS for the board. $299 all in, and they are now including a relay board (which you probably won't need).
I think all you would need is a PS for the stepper motors. I'd sure give them a call or drop an email. Probably would work with the OE steppers, with some tech support.
You can trace down the limit switches etc by flipping the cabinet on it's side and removing the bottom and back plates. I started there and ran the wires to labeled terminal strips.
What am I missing?