I would definitely make the board bow first. It will be a cheaper lesson, and you will have all the information you can absorb with the simpler project. There will be plenty of info that will carry over to stave bows. I think tillering is the main thing to see done and have explained, its hard to read about tillering and what to look for, and get it right. That, and how to actually use hand tools properly. You'd be surprised how many people will pull a rasp over wood on the return stroke, not knowing it cuts only in one direction. Or not knowing what a scraper is and how it works. Stuff like that, you'll get with the cheaper board bow lesson. You can always read the additional stuff about stave bows, backed bows, etc. and ask questions here as you progress down this path.
As for power tools, they don't do anything a hand tool won't. They just allow you to do it faster, with less effort. So keep that in mind if he shows you methods using power tools.