Probably best to put a message in every forum. That way you'll be sure that everbody sees it!
No, don't do that, it would be seen as spamming.
There's no formal introduce yourself area, but sometimes you'll find a thread for that purpose in some of the players forums (for the fans obviously). For example, there's one in Maria Sharapova's forum, same for Daniela Hantuchova, Venus Williams, Kim Clijsters or Amelie Mauresmo, just to name a few. In a more general way, any discussion on topics not related to tennis must be started in the Non Tennis section of the forum. There you'll find a list of chat threads, where you can present yourself to the other posters. Of course you can also start your own thread (but in the Non Tennis section only).
Do not hesitate to ask for any more information