The concepts aren't hard, and it is sufficient to understand the concepts to pass, but knowing the details to get a high score is tough - memorising countless drug names, anatomical terms, self-care facts, developmental theories etc on the off-chance that it'll be on the exam.
The hardest aspect of the course, IMO, is memorising or understanding things in a manner that will serve you well in the future. The whole point of our course is to be good doctors, and there's no real point memorising all this stuff in first year that is unimportant or you will eventually forget when you actually start practicing. So learning the information with the long term view of retaining it for the future rather than just to pass the upcoming exam is the most difficult. (I tend to cram facts then forget them after the exam, like for VCE History. It depends on your learning style.) Which is why there is a heavy emphasis on clinical applications in the course, I guess. You tend to get bogged down by all the minuscule details that it's easy to lose sight of the big picture. (especially for anatomy)
As for your other questions regarding contact hours, 25ish is my approximation, but things like crazy illogical 5-hour breaks, extra reading/study and hanging around the anatomy museum would probably up that figure.