Welcome! Your goal is inspiring - and most certainly a reachable goal. You have lots of time to plan and train, especially if you are motivated to begin now.
Swimming - you need the basics - look for resources such as local YMCA, swim clubs, or Masters swim programs that offer instruction, lessons, or structured coached workouts. At first you might feel like you'll never learn and you might get bored with endless technique drills but the time you invest will pay off. Do not concern yourself with distances or speed until you have mastered basic techniques, which may take you a full year, or possibly longer.
Cycling and running - focus strictly on building your aerobic endurance base. Follow the training plans on this website - they are quite good. Your Trek Antelope is all you need - assuming it fits and is comfortable enough for you. Use your spinning classes as needed and take increasingly long outdoor rides as you build up your cycling endurance. Run a couple times each week, slowly increasing the distance of your long run each week. Every 3-4 weeks, ease back on the distances and take a 'recovery' week.
Strength - look into strength training exercises that apply to triathletes - core strength and weights with higher reps/lower weights. Lots of online sources here, I'll see if I can find some. Do this regularly throughout your training.
Nutrition - as you start to go longer in training and eventually in racing make sure you don't ignore the important role of nutrition. Pre-exercise, during exercise, and post-exercise/recovery nutrition should be carefully planned.
Racing - you will want to get a number of sprint triathlons and possibly even some Olympic/International distance races under your belt before you do a 1/2 IM event. See what races are available for late season 2004, or early season 2005, and sign up for one that is within your capability. This will give you a short-term goal on which to focus and you'll learn LOTS of important tips along the way. Do a few other sprints and/or and Oly/Int' distance race next year. By then, you'll feel like a veteran!
This forum is a great resource - use it often!
Good luck - looking forward to following your progress!