Other than that, search the web, there are lots of sites/forums that will show you the way.
CCO is a good one, but I find THO is very good, the folks there are not as "sensitive" as some on CCO!
Yes.. matter of fact, if you buy the bushing kit from HUT, it's designed to work on the pen mandrel... the "bushings" are actually expandable rubber bushings that fit inside the drilled blank, and are expanded by tightening the nut on your mandrel.
Here is another site with kits and supplies for game calls http://www.webfootcustomcalls.com/
Thier soundboards are suppose to be better than Huts. I have not tried them yet but plan on it soon. They also have the soundboard jigs that are cheaper than Huts. The book that Michael told you about is very informative.