In all actuallity, the actual building isn't that hard as long as you take your time and don't try to cut corners. There are certain things that one must do, and proceedures for installing the operating system should really be adhered to as that is where most people get fouled up.
There really isn't that many pieces but knowing what goes where and all is a little bit tricky sometimes. Just depends on the system and how much room that you have to work with.
There are other ways to go about it also.
You could go the "barebones" way where you buy a partly built system from a retailer and then add the other things that you may want.
here is a good example:
or this with OS:
in which you can add to what they are offering and see if this might be a better way for you.
I originally suggested the brand name purchase simply because it is hard to compete with them for a full system at the lower end market. In the higher price ranges ...it is a different story.
here are the links to a few of the sites that I use regularly.Safe to do business with and decent prices. Just look thru and you will get a better idea as to prices of components and name brands.