1st Ironman

Welcome to BT. 

Typical Ironman training plans are 20 weeks long (much longer, and burnout becomes an issue, much shorter, and it's difficult and risky to build up the long workouts without injury).  Most of the plans assume you can run 90-120 minutes, ride 3 hours, and swim 2500 yards AT THE BEGINNING of the plan.

You'll want to build up to a long swim of 4500-5000 yards, a long bike of 6+ hours (100+ miles), and a long run of 3 hours (17-20 miles).  General rule of thumb is to increase longest workouts no more than 10% per week and total weekly volume no more than 10%.  Ramping up too quickly significantly increases the risk of overuse injuries (tendonitis, pulled muscles, etc.)   Typical plans call for average training volumes of 10-12 hours per week with peak weeks in the 15-17 hour range. 

Given your non-conventional introduction to Ironman, consider hiring a coach to develop a customized training plan.  Expensive?  Not nearly as expensive as not racing and paying for months of physical therapy because you injured yourself! 

Start with establishing some goals for the race.  How quickly do you want to finish the swim?  the bike?  the run?  I don't know how much natural talent you have, so I don't know if it's possible to go from swimming 5 laps without stopping to swimming 84 laps in an hour (the top 15% of the field might come out of the water within 1 hour).  Only you can decide which goals are more important to you...I will suggest that the goal of finishing "as fast as possible" conflicts with the goal of "finishing."  A goal of finishing quickly means speedwork and high-intensity training which greatly increases your risk of injury.  Racing on the edge amplifies small and subtle nutrition/exertion mistakes (you're more likely to "blow up" the closer you are to your limits).  A 2-hour swim, 8-hour ride, and 6-hour run will have you finishing in about 16 hours.  This gives you a 20-minute "buffer" on the swim (in case the water is choppy) and a 20-minute buffer for the bike cutoff (in case it's windy or you have mechanical problems).  Targeting these kinds of splits means you'll have a lot of time to "debate" with yourself what you are doing and why you're doing it, so you'll need to spend a lot of your training time convincing yourself that you should stay on the bike for another hour or two. 

McFuzz, excellent response. I'm preparing to get ready so I can prepare my 20-week IMCDA training plan next February, so I enjoyed what you had to write.

Av8torx, good luck on your Ironman training. I know this site has a free 20-week training program available, and I've been impressed with reading the Be Iron Fit book. It includes three plans: Just Finish, Intermediate and Competitive. Might be worth looking into.

Also, just noticed you are from Draper. I'm part of an AWESOME triathlon club here in Utah called the Desert Sharks Triathlon Club (desert-sharks.com). We have weekly training programs for all disciplines and a supportive local message board. You should check it out.