The red river enduro (munster, Tx) is coming up on 10/6 and Cloudcroft, NM is next weekend (lots of rocks). There are many events in the state. Some are more kind to beginers than others, but most offer super short (25 miles or so) No trophy, but it will get you aqanted with what it takes. check out
www.tscec.org for a season Schedule. I would also post this in the message board. There are many in there that will give you a line on the more beginer friendly races. You best bet would be to sign up with someone who has done a few and keeps time. You can just follow along. The TSCEC page also has a pretty good basic explaination page.