Make sure whatever case you get is going to be easy to work in. If things to go wrong, it'll just make your life more difficult. As has already been mentioned, a working PC with a net connection can be an absolute life saver.
I built my first PC quite drunk(not intentionally!) and everything went fine, probably one of the most stable machines I ever used. I don't recommend getting drunk, however nervous you get, but staying calm and not panicing goes a long way.
I very recently helped a friend build one over the phone, and until I suggested hoovering out his old machine, I don't think he had even looked inside one before. Aside from a faulty HDD and subsequent OS installion problems, he got it all sorted in a night. It's all in the groundwork.
Make sure everything is compatible, read reviews. It's half the fun.