First, go to a race, watch and see if it is for you. If you think it is, talk to the promoter to see if they know of any clubs that do some simple intros to how to get on and off the bike in an expeditious manner. Talk to the people at the race and ask them questions, etc.
Then, if you want to do a cross race, go for it. Cross is a fast paced, anaerobic activity so be ready to blow your lungs out! It is really fun if you are into that kind of thing!