Have done it the past two years. I don't have any regrets although I'm not doing it this year. Partly because I DNF'd last year with 20 miles to go when another rider crashed into me and partly because I'd like to ride the Austin to Shiner Century. It is a great cause and a great experience though. I'm sure you will enjoy it, just be sure to keep an eye out all around you. If you're not comfortable riding in a group, don't try drafting others during the event.

My best advice is to work on climbing. Although it's not as hilly as the Houston to Austin, the second day is surprisingly hilly with a couple of short, steep climbs, and a long(ish) but shallow one up Eagle Mountain Lake. I saw lots of people having to walk their bikes up on the second day. There are a slew of recommended training rides throughout the year, and a couple of weeks before the event, there is an organized and supported long ride in Plano that's free to all. Follow BikeMS_DFW on twitter, they frequently had weekly training rides organized. Good luck, I'm sure you'll have a blast. It's a great event.