New World of Darkness rules

[Jeivar]

EDIT: Changed the title to be about NWoD rules in general.

Okay... so, I'm going to be ST-ing a game of Princess: The Hopeful (a fan-made splat for NWoD) in a couple of weeks. Only, none of us owns the main book. We ARE all familiar with the system, and understand the basic functions, but could someone be kind enough to give me a basic rundown on which Abilities go with which Skill? I would have, for example, thought that Medicine went with a cerebral kind of skill, but a Princess healing Charm requires a roll of Medicine+Dexterity.

Also... dice rolls in general? Does a roll of 1 still subtract? And under which circumstances do you reroll a successful roll?