Cost and knowledge needed to build a desktop with these features? Or is it better to buy one already made?

Our Windows Vista computer has decided to spout off lots of blue screens and appears to be dead. At best it stays on for a couple of minutes before blue-screen error messages show up.

So I'm thinking that we need a new desktop. Our daughter is in 7th grade and would like to start making/editing movies, and she already draws a bunch and would like to start creating animation as well. I'd like to get a desktop that won't be ridiculously expensive, but I'd also like to pay a little more to get more life out of it.

I know little about computer guts, but I don't mind trying to build my own with the advice of Youtube, computer sites, and questions to a friend at work in our IT department. But if it makes sense to buy one from ASUS or HP or Apple, I'd consider it. I get a minor discount at certain places (like Apple and Dell) because of my employer.

I would like to get a Haswell i5 at least, but I really hadn't thought about replacing the desktop until it forced me into thinking about it.

Any suggestions, specific or general, about specs (graphics-integrated or not, how much RAM, what type of drive, Windows 7 or 8.1 for a desktop if I don't go with Apple, etc.), the ease of building your own machine, and whether it's worth the time, are all appreciated.