Hi - I agree that everyone has given you great advice. I think you are awesome for doing your first tri! I took forever in my first transition at my first tri - it's not a big deal. So, just bring whatever you like for the ride and run and slip into it at that transition. As for running shoes, there are shoes that are for 'heavier' runners that give good support. I would suggest going to a good running store with knowledgable people. I know there is a "road runners sports" RRS brick and mortar store in San Diego. They have a huge selection and people generally know what they are talking about. Just one option... Ca has tons of good running stores. I put slicks on my mtn bike for indoor training in the winter, and it's easily (and cheaply done) - though you may consider borrowing a hybrid from somone particularly if you have a really cushy front fork and rear suspension. Those things eat up a TON of your forward energy. Um... what else? Will you be swimming in a wet suit? they give you extra float and really help in the swim (check to see if they are legal for your race). You can rent them all over the internet and there are good threads here on that. If the swim is a big everyone at once start, and if it's a big race, I would suggest starting on one of the sides so you don't have uber competative dorks trying to swim over the top of you. Good luck - let us know how it goes for you!