1. yes, but i'm only giving you the general stuff. if you're ready to build. then i will give you more detail stuff what you need to buy since you have to make sure all the parts are compatible. for example, if you're using intel chipset, then you need motherboard design for intel. also the chipset socket number needs to match with the motherboard. some newer motherboard only support sata because IDE is too old and slow, so if you're buying a hard drive and CD-ROM, you need to buy only the sata one as well.
watch this guy. he will show you the basic to build a computer. http://www.youtube.com/watch?v=uUY0tP5jYIo
anyway, the way he applies thermal paste on his heatsink is wrong and among other things. also in this video, he's using integrated heatsink that come along with intel chip. if you want to overclock (make the computer faster than its default), you will need a third-part CPU heatsink like the white LED you see on my computer there. also this video, he's using only 1 hard drive. for RAID configuration, you'll need at least 2.
my pc build is more complex as i have an SSD (solid state driver sata III) as an operation system bootable drive while i have 2 WD hard drive in RAID 0 configuration for storing and install game and software, plus a separated hard drive for backup. so if you want to build like me, you would need 3 hard drives and 1 SSD. =p
the rest is simple but each case has different ways to align the components. so unless you're buying the exact case model as that guy in the video, then you don't need to worry about it. but most case have exact function, just different way to place its parts. in mine, i have cable management where everything is neat and cable is hidden. it takes a bit more experience in building computer to maneuver it. =p first-timer, you might want to invest in time look at people computer and see how they build it.
if you want to have somebody build for you, then yeah.. just buy all the parts and bring it to them. however, you don't know how good of a job they build your computer cuz most likely they won't give a $hit about cable management, so it's better to get someone professional and trusted to assemble it for you. that site cyberpowerpc is a professional pc builder. they charge you more if you want cable management and also shipping fee is high too. however, don't worry about it.. don't waste money with cable management since that they should build well cuz fear of customer complain. though, it's important to keep track of warranty.
are you familiar with each computer component function? you need to know before you build it. i'll give you a quick walk-through
motherboard: it's the function to connect all hard drive, CPU chipset, CD-ROM, etc... motherboards come with size model as well. so if you're buying ATX motherboard, then you need to buy case support ATX. there are two major brands in this field, Asus and Nvidia.
CPU: it's the computer brain. it's the chipset to run stuff. Intel and AMD are two competing rival. each chipset come with a specific socket number. for example intell 775, 1366, 1566, etc.. therefore if you're buying an core i7 1366, you need to buy a mother intel socket 1366. intel obviously slightly better.
hard drive: there's two kind of hard drive. one is standard disk drive, the other is solid state drive. solid state drive (SSD) doesn't require spinning wheel, therefore it's much much faster. the fastest standard drive spinning at 10,000RPM is slower than a SSD sata II, let along SSD MLC sataIII. so that's why SSD is the future. though a lot more expensive obviously. Western Digital/Seagate are good standard disk drive. Intel/Crucial are good brand for SSD.
CD-ROM: it's the Cd reader and burner. no need to explain. any brand is good.
power supply: well you need to get a good power supply, above 600watt for gaming since your video card will consume a lot more power than a regular mainstream computer.
RAM: ram is basically virtual memory. the computer programs access and store temporary data to RAM. more RAM, the better. though speed like 2000MHz vs 1600MHz vs 1333Mhz vs 1066 make a different. Any brand is fine.
case: case is important since it's the look and design. there's also different size of case. small, mid-tower, and full tower. the bigger the better, but more heavy. any brand is alright. recommend antec and cooler master.