Sounds great, you should be fine with 10, and that makes everything easier. The simplest way to get the newest build to use his computer to burn the ISO file to your USB; that way, you won't have to worry about the possible consequences of skipping versions (it might be fine, it might not be. You know, like Windows in general). I can write up some instructions for you if you like, but the directions on Microsoft's website are surprisingly helpful.
And I do think it's a good idea to buy a copy, even if you're only doing it for the code. You'll get more options to personalize your install, and you won't have to worry about issues with future updates. But like I said, that can wait until you're sure everything works to your liking.
