I'm pretty sure the motherboard is toast, bulging capacitor. Just powered it down one night and the next morning it just decided to give me a hard time. It receives power, the CPU and GPU fans spin at full blast forever, I've functioning ram sticks, but does not post. I just bought a replacement motherboard for ~200 CAD. Hopefully things work out.
If it's useful for anyone, I can perhaps record a quick video of putting everything back together on request. I've ripped out absolutely everything.