I'd echo what Mr. SR500 said about RAIN. There are plenty of places to go to the bathroom, at least until after the last SAG. I had to use a bathroom at a firestation in some tiny town in 2008. They were nice about it though.

Trust me; bathrooms really are your last concern at RAIN. If you stay hydrated enough past the last SAG to actually need to pee you're lucky! The bigger challenge is the logistics of getting to Terre Haute for the start and home from Earlham College at the finish. If the weather cooperates, it's a great ride. I love doing it.

As for the Hilly, I don't usually do that ride. Too many people for my taste, but I'm pretty familar with the climbing in southern Indiana. I don't know how Heartbreak Hill got its name. Local legend, perhaps. It does hurt a bit because your legs aren't quite warmed up yet and you can count on it being chilly, especially for as late in October as the ride is this year.

For gearing, I'd definitely recommend the 27 tooth cassette. I'm always hestitant to tell somebody that the hills are either easy or hard. There are too many variables that have nothing to do with the hills themselves for me to say that. All I can tell you is that they're mostly short and mostly steep. Some are really steep. The worst that (usually) happens if you can't climb one is that you unclip and walk your bike. Plenty of people do that, and there's no shame in it.

Do I think your 10% gradient is sufficient to help you train for it? Probably not, unless you go up it in a bigger gear than you'd otherwise choose. Would I let that stop you from doing the ride? Heck no. Like I said, the worst that happens is that you walk up a hill. It's otherwise a fun ride and weekend.