It's difficult to give an answer on that.
It depends extremly on your application. In general as more specific code (non JavaEE standard) or special Server specific deployment descriptors as difficult your migration will be.
Also if you have an old application with before JavaEE5 you will have lots of XML to migrate. In this case you should consider to migrate to >EE5 in one step. That will be not a big difference from the efforts and you have better readable code
Thanks for your feedback. Please take an example of Oracle Mapviewer and how to deploy it in JBOSS.
I don't know what "Oracle Mapviewer" is.
If you try to deploy applications in JBoss/Wildfly you can simple drop it to the standalone/deploment directory, it will picked up.
See the documentation for more details.
As this is a community you will find help if you have special questions, but we do not migrate your application for you.