Hi!

Where to begin... :)

- If you are not familiar with java language you should read
some book about java language like "Thinking in Java"
(http://www.mindview.net/Books/TIJ/)
and you should browse http://java.sun.com/ and
http://java.sun.com/docs/books/tutorial/

- I don't know any mailing list for java but I supose there are plenty
of them on internet (google).

- You can find mailing lists for netbeans at
http://www.netbeans.org/community/index.html
I think you should subscribe to nbusers@...
On www.netbeans.org you will find a lot of tutorials for netbeans.

- Can you develop SDI applications with java? Sure, you can develop
whatever application you want :)

- Multitier?
Well, you should first learn java and then continue working with
multitier.
I never worked with JBoss so I can't help you but yes,
you can use JBoss/Hibernate/(Webservice or EJB) combination.
I suggest you to look at GlassFish too (it's another application
server) or Tomcat.
But maybe you don't need application server at all. Starting from
Java 1.6 you have bundled application server
so you can develop your own application for serving web service
(less memory).

- Eclipse vs Netbeans debate?
- Eclipse is SWT based (search in google) and Netbeans is Swing base
("real" java)
- I prefer Netbeans because it's Swing base and UI designer is much
much (really) better than in Eclipse.

Conclusion?
Learn, learn, study, compare, learn... :)

All the best,
damir