time commitment

It'll depend on the chapter. Most, if not all, have chapter meetings on Monday evening. They normally have new member meetings once a week, and you will probably be expected to attend other things like homecoming and stuff. Don't let it freak you out though, it's completely manageable with school and other things, you just need to be smart about your time! Best of luck :)

This would be a great topic to bring up while you're talking to members during the first 2 rounds of recruitment. The girls you talk to will be happy to answer and very honest!
I am a pre-med student as well, so I understand your commitment to grades. I've been able to get a 4.0 gpa every semester as well as hold officer positions in my sorority and have time for other things, including other RSOs on campus. You'll have at least one meeting a week, as well as extra meetings if you are involved with other activites like Greek Sing! You'll have obligations such a pep-rallys and philanthropy events for your house as well as others. As long as you are focused you will have plenty of time to be involved and excel academically.