Football player, turned blob, turned swimmer?

I have always loved swimming and for a big guy was pretty fast in college, after 10 years of essentially doing nothing for exercise and getting plain old obese, I made it all the way to 330lbs. After 6 weeks of swimming and making minor changes to diet (one step at a time) I am down to 315. Being of a competitive nature I need some goals to keep motivated and I landed on one. The goal is to be the swimmer in a triathlon team in July 2008 (9 months to get ready). The swim is 800m. My goal is to complete the 800m in 16 minutes. I am swimming a total of 800-1000m three days a week now but that includes everything (some kick boarding, arms only etc.). My schedule allows for me to train three days a week (may be able to stretch it to four some weeks). Can some one point me to or help me out with a workout schedule for a beginner that still needs to drop some tonnage (70 lbs) and wants to at least semi competivive in my age group on the swim leg of the race? Thanks