I would start with the JBoss quickstart examples for AS7, can be found on the download page http://www.jboss.org/jbossas/downloads/
Also the Getting started is helpful https://docs.jboss.org/author/display/AS7/Getting+Started+Developing+Applications+Guide
But remember that the full EJB3 functionality is not available until AS7.1, I don't look in the example whether you need this for this example.