Hi Rudi,
unfortunally there is no tutorial about the nodeeditor... its still a project in development.
But a good point to start is this forum ore the thread http://moi3d.com/forum/messages.php?webtag=MOI&msg=7777.1
You will find a lot of examples for whats possible to do with the nodeeditor.
An other thing are the extensions - a lot of people write special plugins for nodeeditor.
I will attach my extensions folder - i think its mostly complete. It goes into the nodeeditor folder

Have fun with nodeling!