How soon can I get to "Black Belt"?  -  The first thing to realize is that in Aikido "Black Belt" means you are now ready to learn Aikido.  A good analogy is that you first must learn to stand before you can learn to walk.  The kyu ranks for Aikido teach you to stand....  that is you learn primarily how to take a fall and receive a technique comfortably without injury.  You also learn the basics of techniques and how to move properly.  As for how long this takes: it depends on the person.  The average length of time to shodan (1st black) is about 7 years.  This seems like a long time but Aikido is much more complex than other martial arts.

Does Aikido have tournaments?  -  No.  The nature of Aikido would make a tournament impossible.  Aikido has nearly no offensive moves other than a few basic strikes used to learn techniques.  There are seminars though.  A seminar is a large class that is instructed by a high ranking instructor held at locations all over the world.  Seminars are held for special occasions, annual events and/or testing.