Which version of JBoss/Tomcat were you using before? If you were using a 3.x release, then the directory structure should be quite similar (minus the tomcat/catalina dirs, of course). The deploy directory for your ears/wars etc would be in the same location.
If you are migrating from a 2.4.x release, this may require, depending upon the requirements of your application, some configuration changes. Have a search in these forums if you are migrating from 2.4.x to 3.0.1 - you may find that the information you need has already been discussed.