Building a pc is pretty easy. We actually had sorta a small competition type thing in my CET I class last year, whoever disassembled and reassembled there old 233mhz IBM computer we all got from IBM (aren't they generous? /sarcasm) would pretty much not get ragged on all year long. Not much, but we all tried to real fast. And your looking at the winner right here

. But you just need to take your time on your first one, research the parts, and read a lot of information on them. They have articles in pc magazines all the time on like "How to build your own gaming machine" and such.
And I noticed civilchoas said "RAM, this is your virtual memory". Nice one, lol. RAM is the actual little cards you stick into the RAM slots on your mobo. It's similar to virtual memory, but it isn't virtual. Virtual memory or paging file, is some space on your hard drive used as virtual RAM.
And correct me if I'm wrong but the shader version doesn't have anything to do with your processor speed. Has more to do with your video adapter.
But finding a gaming computer for 1000-1500 shouldn't be hard.