PC building is truly very much easier than most people set it out to be. I know how daunting something can seem at first until you actually do it, but the best advice I can give you is practice first if you can. Then you'll get the confidence you need to do it.
There's just a few simple rules for building a PC 99% of the time really.
1) ground yourself before working on your parts / PC. The most universally accepted way to do this without a wrist strap is to leave the PC plugged in for a moment, touch a metal case component (Side panel, back panel, etc) and then unplug the power supply and work on the system. In my experience, this works fine, even with the servers I work on at work. Also be sure you're not on a shag carpet, or even lineoleum. Static can build on both surfaces and cause ESD (Electrostatic Discharge) which can kill parts with shocks you can't even feel (rubbing your feet on the carpet and touching someone is several orders of magnitude more powerful than even a simple shock that can kill PC parts. Most of the time, you'll never feel it)
If you can get access to a grounding wrist strap, it's pretty much the same principle, attach it to the PC, put it on, and when you've given it a few seconds, disconnect the power cord from the PC and start your work. In cases where you're not yet building anything, leave yourself attached to the case, and work on the system from that point, only plugging the power in after you've completed the build.
2) If you've played with Legos, or any type of "assembly" toy growing up, you can build a PC. Yes, absolutely serious. I showed my mom how to upgrade her system, and even my brother could do his when he was only 10.
3) As long as you read instructions books on things like how to insert processors and RAM, you really can't screw much up. If it doesn't go in on the first attempt, don't force it. Try it another way (with RAM, that's easy, just flip the stick and try again) Processors are usually keyed so they only sit one way. This is true for Intel AND AMD.
4) Relax! PC building is fun! I know as a veteran, it's easy for me to say that, but once you build your own, you'll never want to buy OEM/prebuilt again.
That being said, the system you linked is fine, and will serve you fine for a couple years. the graphics card is a little on the lower side, but it's still an AMD latest-gen and should be fine for just about every game out there right now.
Originally Posted by 5ton
Also some people say to buy a pc built and just upgrade the power supply and videocard. Is that hard to do and worth it?
Systems from OEMs like Dell or HP that might be the case, but iBuypower rarely puts OEM generic crap in their systems, so you shouldn't need to do that with the system you have linked here. You also have to be careful when you buy OEM systems, and pay attention to the warranty terms. Can you open the system to perform upgrades or does that void the warranty? those kinds of things.
That being said, if you want to buy the ibuypower and then use it to start your tinkering, it should be a fine system.