AppServerIntegration: Getting Started?

I am looking to take a shot at developing a Sun App
Server 8 plugin and was hoping to get some pointers
regarding getting started. I have not developed an
IDEA plugin before so be gentle. I know a couple of
you have developed new AppServerIntegration plugins.
Did you use the Tomcat source as the base? Are there
any good docs out there for this, I notice that the
provided JavaDoc is sparse?

Tomcat source is not very useful as a start, since Tomcat is not a full app server but only a web container. Only a small part of app server integration is covered by the Tomcat integration. The two most important things of a full app server integration are manipulating the server-specific deployment descriptors and communicating with the server using JMX. Tomcat integration lacks both of them.

A better starting point is the Weblogic integration. Big parts of it are of course very Weblogic-specific, but it gives some very useful hints. For the development of my JBoss integration plugin I even installed an evaluation version of Weblogic, just to be able to create a Weblogic project and to see how the Weblogic integration works.

If you are new to plugin development then take a look at http://www.intellij.org/ and especially http://www.intellij.org/twiki/bin/view/Main/PluginTesting (thanks Jacques, you saved me a lot of time!).