Take a look at the Q/A wiki page. It's just a start, but it does provide some of the info you are looking for.
It seems like it's not a bad idea to base your tests on the testsuite module. However, it is changing. If you get the latest code from Branch_3_2 of the jboss-3.2 cvs module, you can see where we are heading.
The testsuite/ant161-build.xml will soon become the new build.xml. It makes use of ant 1.6 macros for things such as launching and configuring Jboss instances. See testsuite/imports/server-config.xml for the macros you may be interested in using.