Hi Joey, there is no difference between photographing with say a Nikon D700 and a Mamiya 645AFD. The buttons are different but the technique used is the same. I can say this because I own both. A camera is just a tool, photography is photography. I think you might be slightly obsessed over the system's price tag or its status symbol. The Newbie corner has some great info on how to start learning photography. Or you can join in with newbie photoshoots offered in Gatherings forum.
On your own, you start by reading the manual to learn its controls (which are less complicated than the average 35mm DSLR), and shooting some daytime outdoor scenes to get used to its handling, basic composition & basic exposure. The thing with the Phase One digital backs is the size of the LCD, it's rather small to be able to judge your exposure. You either have to learn to read the histogram accurately or shoot tethered to a laptop. This is one reason why most of us are rather surprised to see this system used as a learner's camera. But the metering on the Mamiya 645 system is fairly accurate, I have no problems with it when shooting film.
I'd advise you try it out yourself first, and when you have more specific questions then we will try our best to assist you. Good luck and have fun!