Sharon you mention semester so is this a university course? The time commitment you mention is very significant for someone who's had surgery and radiation. I understand that attending a course is one way to feel 'normal' and in control - we all need that. Thinking ahead, it may be worthwhile asking about flexibility if there are assignments or any form of homework required. I was working only a few weeks after my masectomy but was involved with planning which involved only one other person. I welcomed the 'normalising' opportunity provided by work.