I'm not sure where I should go in the forums to ask where to get the parts and how to make the circuit board for a RepRap Huxley, or where to buy a circuit board if necessary.

I guess a Huxley may use any of the popular boards used by other RepRaps like a Sanguinololu or Arduino Mega + RAMPS that you can buy the PCB, a kit, or a soldered version off eBay.

The wiki is your friend: [reprap.org]