I just finished my first season with my 1997 H20. If you are in the Central US, you ought to hook up with Divisions 14 and 7. Both have very active 20 fleets. I attended 4 Division 14 regattas this summer and had a blast. I live in Shreveport, LA, most of the other 20 sailors I've raced with are from Texas, Oklahoma, Arkansas and Kansas. As for the spinnaker, I think that would be a fun ride. However, before you spend a bunch of bucks on one, keep in mind that a spinnaker isn't legal for class racing. As far as I know, there's nothing from stopping you from flying a spinnaker in open multihull regattas.
If you are in either region, these websites will get you started:http://www.hobiecatdivision7.org/http://www.hca-na.org/
Put your cursor over the "contacts" tab then click on "division contacts" and scoll down to find links to all the division web sites.
The best way to learn about Hobie sailing and particularly racing is to get involved. The forums are great but the face to face and hands on discussions that you'll get with other Hobie sailors at regattas and other events will prove to be invaluable to your progression.