Anyways, Just get another board that handles klipper and just add it? Is there a specific “USB to Stepper” board, or do I just hotwire in another motherboard.

Most control boards will let you know if they run Klipper in the listed specs and the stock ender 3 pro boards do run it, at least the 4.2.2 and newer boards do. You could probably even run an Arduino with an external stepper driver if you wanted to go real jank but I wouldn’t recommend that as a second board.

I have the Ender 3 Pro with the “magical probably wont burn down your house” power supply, is that enough for another board, if I’m running another stepper?

The stock PSUs that come with the 3 pros are 350 watts and are mainly that big for heating the bed. Adding another stepper to the printer shouldn’t tax that much more.

If you are looking at going the Klipper route there’s a bunch of good install guides, I think Nero3d has a pretty good one and most the big printing YouTube seem to have done one at some point. Just beware they’re usually guides for running the host on a raspberry pi so you’ll have to figure out those parts using your own setup.