What can I expect from A School for MA as a PO1 prior Army?

I had a First Class in a class behind me when I was there, he was a former Seabee, but I imagine it would be fairly similar. You'll be staying in one of the hotels there unless you really want to stay in the barracks. Currently, liberty is pretty limited because some of the new recruits did some stupid stuff a few months back and got everyone's liberty taken, but yours should be unaffected. The school is really easy, pretty straightforward stuff. Most of the instructors are Chiefs and really helpful for anything you may struggle with. It's just the most basic aspects of the job, there's "C" schools for the more specific jobs like MWD or Corrections.

It should be fine for you. Not a long school at all and it's super easy to get a grip on things and learn.

If you are a former Army MP, then the MA school would only give you the differences in forms, etc. between the services. If you were not an MP, then the MA school should offer you a lot. One of the big differences between Army MP and Navy MAs is that as a senior Petty Officer or Chief Petty Officer, you could stand the chance of independent duty where you are the ONLY police officer for the command. You really have to good at nearly every facet of law enforcement and security.