I learned yesterday that if you look at someone else's lab, even if you're not copying directly, it can still be considered academic dishonesty. People usually won't do anything about it if you're not copying, but it's still really sketchy. It's the same with old tests that the prof hasn't consented to release.
Aside from the academic dishonesty thing, I worked very hard on my notes and labs (and one of the assignments...not really the other
) so I would never sell them.
If it makes you feel any better though, the midterm is really easy
It's honestly the easiest part of the course--much better than the assignments/labs/exam
You'll do fine even without an old version.