Q for all part-time Apple Specialists: time commitment per week?

Hi! I recently interviewed for a specialist position with Apple Retail, and I originally applied as a seasonal worker, but they don't take seasonal workers. However, they offered to let me work part-time during the school year. With that said, how much time do you spend at the store each week? I've been told by one of the store leaders that they expect something like a couple of evenings during the work week and all-day during the weekend.

The reason why I'm asking is that I'm not sure if I can handle my courseload (I'm a sophomore in university, bio/pre-med major) + extracurriculars + a job with Apple.

Thanks so much for your help.