There's a lot of ways to go, but I'd skip Hort if that's not your thing. Subbing out the plantscaping can be a good thing if you find the right business to parter up with. They will send you at least as much business as you give them.
A business degree would be useful but don't overlook the liberal arts-hardscape clients tend to be well-educated and you need to be able to communicate with them on their level.
I think the best way to learn hardscaping is by working in it along with getting manufacturer and trade certified in paving, walls, lighting and water features. I just got back from a great hands-on waterfall seminar and I probably learned as much from the other guys talking as I did from the instructor. The internet forums are a great source of info as well. The fact that you're on here participating at 19 says a lot and I suspect you'll do quite well.
www.land-arts.net