A) Do you have a road bike as well as a track bike? You will need one, since fixed-gear bikes aren't allowed in mass-start races (crits & road races.)
B) Sounds like you probably have a decent base of fitness. Next thing you should do is find a group ride you can join, where you will be able to develop group riding skills - essential for mass-start racing, both for your own safety and everyone else's. If it's a fast group, you'll also start to get some experience with the effort required for racing, which is very different from what you would do on long solo rides.
C) Look here:
http://www.bikeforums.net/showthread.php?t=380788
Good luck!