I took 1G03 in my first year (not as an elective) and found it really interesting. It's very "Health Sci" in its structure, meaning that instead of exams you'll have plenty of groupwork and written reflections. I wouldn't say that it's difficult, but just be aware that its not what you'd expect from a "normal" course. If you're interested, then definitely look into taking it.
I can't say for certain whether or not it'll increase your GPA. If you put in a decent amount of work, though, you can definitely pull off a decent mark. Just be aware that a good portion of your mark is (a) somewhat subjective since you write papers instead of tests, and (b) somewhat dependent on the group members you work with over the term.
Looking back on the course, which I took almost three years ago, I remember enjoying it quite a bit.