The two most helpful things you need to know: newegg.com & google.com. I realize the irony of directing you to websites when you are talking about building a computer; without a computer you can’t access the internet. Go to the library, or a friends house. You can find everything you need to know about this on Google, then order your parts from Newegg. Newegg is not always the absolute cheapest, but usually they are. They have a good selection, good customer service, and great shipping. I have made a lot of money fixing computers for people by showing up, searching google about their problem and then following the steps for the fix. The crazy thing is, even when I recommend this to the people that want to pay me, they still ask me to come.