Geeetech

I would like to implement auto bed leveling using an aluminum heat bed. Will the Geeetech i3 Pro C support the power requirement of the Mk3 aluminum heat bed without any modification? I have seen lots of articles where people have stated it draws more current from the power supply than the Mk2b and there could be a risk of it damaging the control board. Many people also seem to connect it with a separate power supply with a relay.

The resistance of the heatbed on I3 pro C is about 1.2-1.5ohms, and the rated power is 96W. And the hotend is 40W each.
So you need to mind those values of your MK3 heatbed. Better to use another PSU.

Okay, I have a couple of questions. 1) I am not really an electrical guy but I can follow instructions. I have spent the last day looking for a good easy to follow "how to" guide on wiring up a secondary power supply for the heated bed. All I can find are explanations such as "hook up the power supply with a relay in between" ???? and 2) Rather than have 2 power supplies, could I just get a PC power supply with dual 12v rails and run the heat bed off 1 rail and the rest of the other? The one I am looking at has 23A on 1 rail and 20A on the other.

yeah a PC power supply will do, as long as it has a 12V output and the power is enough.