I'm a first timer too but, yes to both. They use your My Schedule to help get an idea of the amount of people who are interested in the session, for seating and room size ideas.

However, the sessions themselves are still 'first come, first serve' so even though you add it to your My Schedule you still want to arrive for it nice and early so you can make sure to get in.

Make sure and watch Joey and Rick's Countdown shows and they answer a lot of the questions us first time attendees have.

http://channel9.msdn.com/Shows/The-Countdown-Show