This semester I'm taking fundamentals, pharmacology, med/surg, and pathophysiology, and I have found fundamentals to be the easiest of the four. You do need to pay attention in class and at least skim the readings, but I found a lot of our test questions to be nursing common sense. Understanding the fluid and electrolytes portion does take some extra studying, but just do a lot of practice questions, memorize the normal lab values, and you'll be fine. I didn't find fluid and electrolytes to be nearly as difficult as I was expecting, from what I had read on AN.
Med/surg is a whole other story! We never really know what to expect on our med/surg tests. Our professor covers SO much material and we are often asked random, specific questions on our tests from material that makes up maybe 2 sentences out of the 100 pages of possible material from our textbook. I feel like med/surg is a mixture of everything. We go over pathophysiology, normal physiology, nursing fundamentals, and even a little bit of pharmacology one body system at a time. But our focus is always on the older adult.
Everyone has such different clinical experiences, so it's hard to generalize what your first experience will be like. For my class, on our first clinical shift, there wasn't much we could do to help the nurses (we had only been signed off on bedmaking, bathing and changing patients, and taking vital signs), so we mostly just helped the PCTs or just shadowed the nurses - more watching than doing. Your first shift will probably be focused on orientating to your clinical site and performing the very basics of nursing.
And it's likely there will be students in your class that annoy and frustrate you, but it's not necessarily a given. After reading posts on these boards, I started NS expecting to see a lot of the types of people that posters on here complain about. However, I was pleasantly surprised - my classmates are amazing and I have the utmost respect for every single one of them. But we are all post-baccalaureate students, so maybe that has something to do with it. Just make sure you don't judge a book by its cover. Be kind and helpful to all of your classmates. You never know when you might need their help someday (especially in clinicals or with difficult projects). It's amazing how much better NS can be when all of your classmates support each other!
Oh, and you have nothing to worry about, nursing school will NOT be easy!