Mary,
I would like to echo your comments and also add that racing, at any level, makes one a better sailor. When you get to race against the best, though, you really accelerates the learning.
The difficulty for many of us, however, is entering into a race when you know that the top sailors are on the billing. Most of us struggle with insecurities of one type or another. When going up against the "best", it requires us to let go of a fair amount of ego and not worry about a poor showing or making a few newbie mistakes. (I know that it has been a big issue for me, especially as one who got turned on to sailing at such an "old" age.)
My advice: Get out there and sail with the best if you have a chance. Professional or amatuer. Everyone's got something to contribute.