Just as an aid may I suggest everyone who is looking into casting spend some time over at
Cast Boolits. I have spent about 6 months reading what all the casters have to say over there and have found them to be as large a source of information on casting as here is on just general preparedness. They also have a 200 something page ebook for free download with allot of casting info. I read that first then dug into the website to find out what all the new terms meant.
The also have a swapping section, have vendors who do custom molds, and allot of other resources for the caster.