Road Bike Racing - Want to start racing

I need a couple of tips on how to start racing.

I'm 21 and in good shape. Been riding long distances for about 2 years (week-end rides) and commuting full-time for less than a year. I've ridden at 22 km/h over 6 hours with full rear panniers on an already heavy steel bike, and I can maintain a 27 km/h speed over a 1-hour ride when riding fast.

I want to know:

1- Should I start riding on group rides before racing to improve average speed and pacing skills?
2- If I were to start racing now, what category would I fall under, and how would I compare to the other riders in that category?
3- Do I need any sort of special training to be at least competitive in a low category?
4- How much faster would a decent bike be (not too expensive), considering I currently have an old and heavy steel road bike?

Thanks in advance for your help!

i would start by doing group rides to help your paceline riding and speed.
also find out if a local club holds short crits in your area. A club in my area has two crits a week (one for novice and one for everybody else) and it only costs $5 to go and you dont need a racing license to take part.
that to me would be a good start and is a cheaper way to find out how you stack up and if you like the racing experience than buying a racing license and not using it.