Hi Rachel, and welcome to TE!

Wow, a Trek 5000 WSD -- nice bike! I have a Trek 5200 WSD and love it. It should serve you well on what I hope is the first of many centuries for you.

Sidi's -- very nice! You seem to have good taste in bike stuff! It's pretty hard to go wrong with Sidi's -- they tend to fit well and last a long time. But now's the time to try on other shoes for comparison sake. I own a pair of Specialized, and have owned Diadoras and Duegis in the past. Fortunately, I don't have issues with hot foot, so I do OK with just about any shoe that fits my small foot. I bought the Duegis in the early '90's, and they have zilch in terms of arch support, etc. Nevertheless, they're still comfortable for me on rides -- even a century.

Helmet -- not good to get a headache everytime you wear it. What brand is it? Some brands fit differently. My Giro fits a bit differently than my Bell. Is there a bike store around where you can try on different brands of helmets? Also, the Giro helmets tend to be pony tail friendly -- thru the rock loc. I think the Bells may be less so, as they have a ratchet back there, and I'm not sure if there's a space for a pony tail. I guess my advice is to try different brands to see which works best for you fit-wise and pony tail-wise.

Spinning -- I think it's excellent. It works the same muscles as riding. When I was training for a century, the weather was bad, so I could use indoor rides to get the miles in. With spinning or indoor cycling, you can do different types of workouts (recovery, intervals, etc.) in a controlled environment (no hills, stoplights, etc.) You never stop pedaling, whereas during riding "in the real world" you have to stop at intersections, and you probably tend to coast more than you realize. Spinning doesn't help you with bike handling skills, though, so it's best not to rely entirely on it to train for a century if you're a new rider. Also, spinning isn't necessarily cross-training, in the sense that it doesn't work out the muscles that cycling doesn't exercise. You might want to do some upper body/core workouts to supplement the cycling/spinning.

Again, welcome to the forums! When's your century? Which one is it?

Best wishes!

-- Melissa