You said,

"I'd like to slowly convert"

You've already got the idea. My first thought as to what you could do is think that plants might be ready to go in NEXT year at this time. I would spend real time reading and looking at pictures 'til I got a grasp of what it is that I'm trying to accomplish.

Even if you start with an Ortho type book or maybe Sunset, these will work you into the mood of contemplating your part of this earth where the garden will evolve. Of course, it would be great to read Saito's "Magic of trees and stones", but it probably won't be available except by a purchase (maybe $100). Don't worry about doing the "wrong" thing. There are many lurking here who will keep you straight. ;-)

Meet your rocks, is there a slope or berm already there? Will there be a natural place for a stream or pond?

Put it all on paper and then think very small (for place) and very long (for time). The idea is to have fun and passion about the whole thing.

Dave

Try googling New York Japanese Garden

Here's a link to get you started:
The Japanese Garden at Pocantico

-Audric