Your grade for this course truly depends on the professor. Office hours are really important for that extra help, and Professor Farhat wasn't super helpful during these. She is a super fast lecturer and doesn't really know how to answer questions. I'd advise picking another professor.

Calc III is hard, don't let people tell you otherwise. It can be tricky in terms of knowing how to set up problems and working through long integrals. Unlike in Calc II where you spent a lot of time doing mostly the same kinds of things (integration of various forms) in Calc III you move very quickly through many topics that are inter-related, but still you really have to go to class and do the HW to be up to speed. You're probably taking this because it's a requirement and professor Farhat is a really good choice for it. I thought she was a really great lecturer and was clear about concepts. I always felt I could learn by simply going to class and while I would read over the book too, it wasn't necessary. She covers a lot of material and writes difficult exams that really test your knowledge, but she is fair in grading and the process makes you really understand what you covered. I've had her for 2 classes and her style is to not collect/grade HW, but rather each class there is a 5-10 minute quiz on the last HW material which you can do fine on if you did the assigned problems.