Chock Ice,
My info is dated as I received my CFI &CFII many years ago. I would suggest you contact, through the web, Flight Safety in Miami. They can provide you with the qualifications that you will have to meet. I don't believe you can obtain any FAA instructor ratings without FAA CPL and IFR ratings. Additionally you will need a M-E rating on those tickets to be a M-E instructor. Actually any flight school,from the u.s., that appears on the web can give you the info. All FAA exams, that I know of, have study guides that provide the answers. Its a matter of studying the questions and answers and then recalling them on the exam. The big "deal" is the required check rides. Thats where the FAA differs from the CAA. Its the proctical that is difficult to get through. If you already hold a CAA CFI then it should be no problem, as the theory is pretty much the same and exercising it should cover the oral part of the FAA flight check.
Good Luck.