I'll be honest with you,
PC building can be very frustrating, despite what people say. You are going to be very nervous pushing that power button but it probably will work fine. Also, expect problems not far down the road, On first boot Audio and screen Res are going to be totally wrong, you'll need to fix those and then cable management is hard, also triple check compatibility and make sure you order from reputable sellers, doing those things will make building a breeze. Building has its frustrating moments, it's not legos, but it took me, a 14 year old, 2 hours to build. Fairly easy.
Newegg - Amazing
OutletPC - amazing
Superbiiz - 2/5 stars from me, sold me a bad keyboard and wont accept refunds for opened items. At least it arrived...
You must realize things could go wrong, but you can easily fix them. Also keep your windows CD and key very safe, I have had to reinstall windows 3 times since i build my PC, and turn off windows updates, those go wrong very easily and will lock you out forever, unless a miracle happens.
Good luck with your PC, don't let these discourage you, I say these so you will know what to expect. Take precautions and you'll be fine. Windows 8 looks good but it has terrible fuctionality, updates making me wipe my drive and less features than windows 7.
Tip: use the audio connectors in the back of the case rather than the front panel ones. Those don't work with headphones.
Windows updates = Evil (I wasted my saturday (today) fixing my PC because of a bad update.)