JAA is very cheap, easy and a whole lot of fun. FAA is the same just spelt differently.
JAA will cost you a few thousand quid whereas FAA will cost a few thousand dollars.
Not sure about the conversion. if i was you i'd fire an email off to the CAA. They will send you a very informative and easy to read reply with all the exact details your looking for.
After you get your licence you should post back on here and someone will give you a very high paid job.