Have you done ground school yet?
Most instructors don't seem to like teaching simmers - you can get yourself into some bad habits if you're not careful. Useful for practicing navigation and some other skills but useless for handling.
I don't think my simming was too harmful but if you have time then concentrate on books. If you can arrive ready to sit air law then it will be a real boon.
Yes, there are lots of different c172s. Your flying school should make their manuals available to you.
Are you sure you want to do a cpl rather than atpl?