Since nobody answered my questions, I guess I'll have to answer them myself.
So, what I really needed to hear in order to implement the SSO on my JBoss was the following magical term : "JBoss Negotiation".
JBoss Negotiation is a JBoss component that has the Kerberos/SPNEGO funcionality needed for SSO integration with Active Directory.
The component is shipped together with JBoss 7.1.1 (which I used), but you can also download and use it independently.
This article helped me to realize that JBoss Negotiation was just what I needed :
It's also a great place to start if you are interested in other types of SSO on JBoss.
You can learn about all the things needed to configure your JBoss Negotiation component in the following articles :
And that's about it.
I think that this is more than enough to get you started.
Hope I helped someone.