I would replace the carriages, and rods, and I think that's what I want to do next, but I can't print anything accurately enough. Is someone willing to print those parts for me, and I can reimburse them? Or is there a place where I can just order these?

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Printer is doing better than it used to, but something's definitely not right. Been trying to diagnose the problem with just information I can find online, but it's difficult for me to just choose a route and get to work.

Biggest problem right now is still the Y motor I think. Circles are misshapen, normally "squashed" along the Y axis. It runs smooth, except sometimes it just "skips" and starts printing in the wrong place, ruins the whole print. This is not very often, but it seems to happen to like 2 out of 3 prints. I've been trying to tune the potentiometer more and I think I'm getting closer but it just takes a lot of time and patience to do that because if it makes just one skip then I have to start all over again.

These belts and carriages though, absolutely suck. First of all the 1.5mm hex screws are stripped so I can't do anything with that, I just want to replace all the rods. The belt is attached to the Y carriage by some horrifying bolt and washer mess, I'll attach a picture soon.

I would replace the carriages, and rods, and I think that's what I want to do next, but I can't print anything accurately enough. Is someone willing to print those parts for me, and I can reimburse them? Or is there a place where I can just order these?

The new stepper drivers came in the mail today (got five of them, you know, just because.) Swapped a new one in for the old Y driver and it works great! Been tuning it, I think I have it where it needs to be, I plan on messing with it a little more just to make sure it's good. Everything else appears to working great. No more flickering lights. We'll see how the first print goes.

Thanks so much for your help, everyone!

did you ever try re calibrating the driver after PSU upgrade? some are very easy to over/under powre motors depending on supplied power. this step will need done anyway with new controller also.

Do you mean adjusting the potentiometers via the screws on the drivers? I tried adjusting it for about an hour, and just couldn't seem to find a spot that worked, or even got close to working.

I didn't know you could just unplug the stepper drivers, that makes it much easier to replace then. It's pretty cheap, so I'm going to try that before anything else. Is there a simple, easy to understand walkthrough for how I would do that? If I'm just replacing one stepper driver, should I just reinstall the firmware? (I don't know how to do that, because I didn't build this thing)

Safest way to do it is to swap them out with the power off. On the back of the drivers, you will see a few notes like "Ground/GND". Make sure the ground pin matches the orientation on the board itself...some stepper drivers need to be flipped 180deg, some not. And no, you don't have to flash the firmware for this change. But if you swap for a DRV8825, you need to adjust the EEPROM settings for that motor.
Fastest way to get a new stepper driver is at Fry's or Microcenter if you have either close to you.

Anway, you could plug your motors back in the way they were, and try swapping Y and Z steppers, as that would again narrow it down to board or stepper.  Perhaps wait until a more experienced member confirms that this is wise, since those steppers could have different potentiometer settings.

These are the steppers: http://reprap.org/wiki/Pololu_stepper_driver_board

If you would prefer a new board, Makerfarm.com also sells RUMBA and RAMPS board. Both are very robust and easy to flash/upgrade. I have more experience with the RUMBA, and I can say that your stock SD plugs will not fit. This means you either splice (solder) the new wires (new wires optional) to use the RJ plugs, or you can use the screw terminals for the motors, heatbed, hotend heater, and power. Plugs for the fans and thermistors should work fine, but make sure you have no less than 4 2pin jumpers for the endstops. You can reuse your old working stepper drivers to save time tuning, just grab an extra one for your inoperable Y.

Not necessarily. The problem could be that the stepper driver went bad, which can happen.

I switched the X and Y plugs and the Y motor moves great, X motor does not move at all, I think it is the driver. Is it possible to easily upgrade the motherboard, without having to do much soldering? I don't have those tools, but I could find someone to borrow it from if I need to. But I'm willing to spend a little bit of money if it means getting a more up to date motherboard.

EDIT: If the problem persists with the motor that I swap out (whatever one is attached to the Y step controller) then what will that mean? Will I need a whole new board?

Not necessarily. The problem could be that the stepper driver went bad, which can happen.
If that is the case, be glad you have the Sang as it does not have integrated stepper drivers. It is very easy to swap them. If it turns out you need a new one, I recommend makerfarm.com

If you don't have any already, grab some white lithium grease. Not the spray kind, the stuff in the tube. This will lubricate the bushings and you can also use it on your Z rods.

EDIT: If the problem persists with the motor that I swap out (whatever one is attached to the Y step controller) then what will that mean? Will I need a whole new board?