Ok, so I just mounted my power supply, but was wondering if it was better to mount it downwards, my case has rubber standoffs for the power supply to stand on, and a vent/dust filter below for it to fan through, although it will be sitting on carpet, so keep that in mind.
Also, what are some good resources for pc building/wiring(inparticular) help?
If you are putting it on carpet, do not put the fan facing down. It'll get clogged and broken in no time, regardless of filters.
I would however recommend putting something down like a tray or even a large mouse mat. Then you can mount it downwards and the PSU will have a much better life.
If by downwards, you mean fan down to draw air from outside the case, then yes, you can. You might have to slightly modify the mounting holes for the screws(mod the case NOT the PSU), but no big deal really. Youtube is a good source for How-To videos, just search for PC build tutorials.