Welcom, dinabean!

Just wanted to jump in on the cadence question. I ride a 7.3fx, and I spend an awful lot of the time in the very middle of the gear range-- that's the middle ring up front, and 4 or 5 in the back. Why don't you start there, and if it feels like you're really pushing hard, if you're feeling a lot of strain in your thighs, and if you can't pedal very fast at all, shift lower until it feels easy. And if it feels really easy, shift up. Really, don't be afraid to shift and shift and shift-- the levers are right there by your hands!!

Maybe one way to put it, the right gear to be in is one where you feel some resistance when you pedal, but it doesn't feel like a strain. And that can vary from day to day, even on the same road, depending on the wind and how tired you are and so on...

Enjoy your new (to you) bike!