[Build Help] $400-500 PC for Gaming, using only parts from Amazon.

Doing some research into building a PC that will run Far Cry 3, Dishonored, etc., pretty well (High settings, not Ultra, 60fps, 1080p ideally). $500 is the upper budget, but I'd prefer to keep it under. Is this even feasible?

I haven't built a PC in 10 years, so I have no idea where to start--I went to pcpartpicker but was overwhelmed. Any starting advice?

I'd prefer to stick to Amazon (I have some gift credit), but if a piece or two come from another vendor that's fine, but I'd like to do a max of one vendor outside of Amazon.

I already have a copy of Windows 8 btw, so the OS isn't a problem. I'm not interested in a disk drive either, unless that's absolutely required.