I've been running for several years and ran my first marathon last year. Since I tackled that challenge last year, this year I'd like to do a triathlon. I'm starting to read up on training and am overwhelmed by all the gear the articles say I need. All I have is a bathing suit, a mountain bike, a good pair of running shoes and a YMCA membership. What do I *really* need? I'm aiming for a June triathlon, sprint or Olympic distance (I'd like to do Olympic distance if possible but I'm willing to do a sprint distance if Olympic distance is not realistic for a first tri).
You have everything you need to get started in triathlons! You have a bike, you have a swimsuit and running shoes.
In regards to the distance… I would highly recommend starting off with a smaller sprint triathlon as your first. The open water swim is quite different than pool swim. Transition from swim to bike can be a challenge, and the bike to run transition can be a very interesting experience the first few times. Use this first race as a learning experience and then plan your Olympic later on in the season.
If an Olympic is realistic for the first year or not really comes down to your athletic background. Being that you've ran a marathon, let's assume that you have a good base. What about your swimming and bike experience?
You have everything you need, except a few relatively cheap basics (goggles, swim cap, bike helmet). I would recommend doing a sprint, then you will have the feel of transitions. It can all be a bit overwhelming at first. After you get a few triathlons under your belt you can then start to think about upgrading or getting more equipment, like a road/tri bike.