1.   Will someone be contacting me and telling me when I have to register and when deadlines are for things like GRO, paying fees, etc.?

When you enter the University, we treat you as an adult. And as an adult, you are responsible for knowing when the University's deadlines are.
Deadlines are listed in the Schedule of Classes and the University Catalog.

If you have questions about deadlines, please see an advisor.

2.   I was very ill last semester and missed a lot of classes. I notified instructors that I would have to miss classes, but some of them didn't allow me to make up the work so I failed some classes.
      Is there anything else I should have done? Anything I can do now?
Whenever any kind of problem arises that affects your academic career at UA, contact an advisor immediately.
You did the right thing to contact your instructors, but that was just the first step. Advisors can inform you of University policies and procedures and what your options are in such situations.
It is possible to withdraw from a class even after the deadline for withdrawal if you are passing the class.
You can file a late change petition, but you must be able to document circumstances beyond your control for the petition to be considered.
Since your grades have already posted, you could file a General Petition requesting retroactive withdrawal.
It is much more difficult to get approval for retroactive withdrawal, but with adequate documentation such petitions will be considered.
See an advisor to discuss your situation, get more information about the options available to you, and get petition forms.

3.   Where can I look up Academic Policies at the University of Arizona?

All the policies and university-wide regulations regarding courses, exams, grades, graduation, registration, transferring, etc. are available on-line in the General Catalog.

If you need help understanding policies, see an advisor.

4.   I want/need to take a semester (or longer) off from my studies at the U of A. Is there anything I need to do to be sure I can get back in?

If you need or want to take up to two semesters away from study at the University of Arizona, there is a process which allows you to come back to the university without having to reapply.
A Leave of Absence form must be completed and returned to your college dean's office.

More information about absences from the University is available in the academic policy section of the general catalog under "Leaving the University".