Also, my psu has four molex 4 pin slots. Would it matter if I used them all to power a gpu? Would I need them for other things?
Molex is typically only used for older floppy and CD-ROM drives, so no it probably won't matter.
Jaguar: Shipping usually is pretty ridiculous for small items like that. I needed to buy a couple molex adapters last year. Online the prices were around 4 bucks and then tack on at least that much for shipping. It was easier to just go to Best Buy and get them for the 6 or 7 bucks that they want for them. Radioshack might work too.