cormacf If you are planning to throw down thousands on a bike just to race consider that a race bike is an expendable item. It can just take one crash to render it scrap. Even if you buy a bike branded from a company with a crash replacement policy it can take months to find a suitable replacement and still cost you more.
A TRI isn't a bike race.
CX was fun for me when I was in shape for it. I always had to travel at least 100 miles to find races and once drove as far as Missoula Mt. for one, it was so worth it. Gas prices and race fees have gone up to the point where I am not going to lay out that kind of cash for a 30-50 minute bike ride.
As far as crits, lots of solid advice so far but the advice to start at the back is asking to get dropped and then get pulled before you get much racing in. High likelyhood of crashing or causing someone else to crash. Bike may or may not be scrap. Your body may or may not have serious injury. If you dig that and the risks are worth it to you, enjoy!