2) Check out Ken Shirriff's extensive documentation on arc2 http://arcfn.com/doc/index.html plus his description of "what's new in arc3": http://arcfn.com/2009/06/whats-new-in-arc3.html
Arc is so young it doesn't have many libraries yet. Some are in Anarki (http://github.com/nex3/arc) and on my site (http://awwx.ws/)