Sharky,
Absolutely do the RAIN. It's a great event, and has a pretty cool jersey almost every year (this year's is particularly badass, imo -
http://www.bloomingtonbicycleclub.or.../rain.html#jer).
Illinois in the morning, Ohio that night - can't beat it! The other nice thing about the ride is that there is a fair number of riders, so you can usually find a paceline that fits your speed. That helps a ton, allows you to conserve energy early in the day so you're more fresh from mile 100 on. Training tip for RAIN - think of it as two rides - a century and a metric. Once you knock out the century, then it's just a metric to the finish. And once you find you have plenty of time to knock out that metric, you can relax and not worry about the clock.
My goal for riders trying RAIN for the first time: Be able to do a century in 8-9 hours without being totally wiped. If you can do that by say, mid-June, you are golden!