So many helpful video guides and written articles on how to build a PC these days. This wasn't like 2000 when you had to read the motherboard, that was in a different language, on how to properly wire the mobo to everything. Today it's so much simpler and easier to do. Like Simon said, you have to be work VERY HARD to mess up the part. Does mistakes happen? Yes. That's just experience and you will only get it by doing it yourself.
The only realistic issues that can occur during a build is 1) if you do not properly ground yourself to prevent static shock (don't build the PC wearing socks on carpet!), 2) spilling liquids all over the build in progress (don't eat and drink in the work area!), and 3) you cheap out on the PSU and it short circuits, frying everything else. That's the most likely mistake a new builder can make. And you can tell a crappy PSU by 1) the stupid low price for the high amount of watts it offers, and 2) read the reviews!