From what I know of PA's duties, I guess you could say they are a step above RN's. ie. you have your CNA's, then your LPN's, then your RN, PA, MD. Not sure where a CRNA, etc. fits into all this.
I believe that PA's can diagnose and prescribe medication to patients, although I believe the prescription is under written by a Doctor (MD) that the PA works under. Where as, an RN would be able to evaluate a patient but would have to refer to an MD to finalize a diagnoses and prescribe the required medications.
I wish I knew more to tell you, but that is a very basic understanding. As for differences in education, to become a PA and go through a PA program you would end up with a "Masters" Degree. At least that is how the programs I have seen work. Here if you have a Bachelors or a BSN you can apply to a PA program which would take about 1-2 years to complete. I did see one college offer a PA program but you had to be an RN with a BSN and have been practicing as an RN for the past two years. That is the only one I have seen, thus far, that required you to be an RN.
Generally speaking, PA's make much more money than RN's. By how much more would depend on the area.
I have seen many PA's working in Family Practioners offices, but don't know what it would be like to be a PA in a hospital, specialized area, etc.
I'm not sure where you are from or how far you are willing to go away to school, but I live in Pittsburgh and understand that there is an extremely good PA program at St. Francis located in Central Pennsylvania, I think. Not sure of the town but I know it isn't the St. Francis that was in Pittsburgh as they have closed down. I have a friend who is considering going for her PA and she mentioned it to me. I think it may be near Altoona, Penn.