1. quarter system = less material per quarter, but more quarters, so it evens out. i LOVE quarters because you change things up 3 times a year, not twice, so it allows for better experimentation and variety.
2. changing majors in letters and science isn't a problem unless it's a competitive major (bizecon, communications studies, etc).
3. no idea about this one...
4. some majors allow you to graduate in 3 years with good planning, so yes, you have time for studying abroad. relaxing is subjective
5. i've heard 5 fiat luxes is a limit... but don't know for sure. you won't really be taking as many as you think you will, but DO try for 1 per quarter. i only took 1 all first year and regretted it.
6. yes, you can choose based on professors. sometimes there are multiple professors for a certain class in one quarter, sometimes there's one per quarter which changes. and yes some professors DO fill up quickly because they're better- check out the math classes for an example