Building it yourself is always cheaper. The one I just built would have cost me almost double if I had let somebody else do it. And the great thing is I built it the way I wanted it and did not have to buy a bunch of crap that I didnt want.
Just follow the directions. Make sure to put in your risers and align the processor right. Everything else is just plug in and all the connectors on the board are typically marked with what is suppose to be plugged in there.