[Mandi90TT]

I prefer bibs for my riding; bibs give you better coverage, and don't cut into your waist. PITA when you have to stop to take a leak, but not impossible.

Biggest thing you have to worry about on long rides (and a 100 mile ride can clock anywhere from 4-8 hours, depending on your fitness level; I do IM triathlons, and my 100 mile rides usually clock in at about 5 hours, depending on terrain) is your nutrition. Make sure you get your body used to eating gel packs and such, as those are the easiest to carry and provide almost instant calories, but you do have to get used to them.

For clothes, I've had good luck with Pearl Izumi and Hincappie for bottoms, and Fox Racing and Pearl Izumi for tops. Pearl Izumi gloves work great for me, as well.

Also, depending on your fitness level and riding experience, 100 miles 2 months from now might be a bit much; a 100 miler (also known as a 'century' in bike lingo) is more or less cycling's equivalent of a marathon.