I'm going to be using Marlin firmware, so that's not a problem. As for the signals they need for operation, how do I find that out? currently it's pretty basic, with 5 steppers going into four ports (Z motors are combined on the i3 Rework), 3 mechanical endstops, 2 thermistors (bed and hot end) and a fan. I am planning on adding auto-leveling eventually.

I can see that the build itself was just the beginning of the learning process. LoL.