omniatlas,
Physio II and Immunology II during Winter semester 2003 were structured one midterm and one final. No quizzes or extra credit.
I also took Eukaryotic Cell Biology, completely different, 2 midterms and a final as well as problem sets every week or so. These were worth about 25% of the grade. This class definitely took up the majority of my time.
I didn't work or volunteer so I could focus on my schoolwork, having been out of the classroom for about 3 years, I was nervous about being a student again. It paid off though, I ended up with 2 A's and an A-. I think I'm still adjusting my studying style, hopefully my Fall semester studying will be more efficient, I want to do more clinical volunteering.
Of those that I spoke to, none held a full-time job, several held part-time jobs, some did volunteering, but most focused on their schoolwork. I'm not saying holding a full-time job will sink you, but it can get pretty rough if your exam days are near each other. Perhaps you can request days off the week before exams? Not trying to scare you, but just to let you know, a majority of those you're competing against won't be holding a full-time job.
Best of luck with your decision.