It's pretty easy if you understand porto, you can get a book online to study it's 20 questions, you don't need to be done with the application to take the test but you will have to be a resident.
To take it you just show up there, for the Rio area the test is at the Jacarepagua airport near the aeroclube do Brasil, you will have to take the flight test there, it's the only place with an affordable plane an old Seneca, other then that there is only an other option in the State of Rio, a C310 in marica (it goes for 700 dollars/hour). An other good place is in Juiz da Fora, but it's in Minas Gerais, they have a nice Twin Comanche....4 hours drive from Rio.
FAA is not even gonna know that you are getting an other license.
All the hours in your logbook that you used to get ratings in the US will have to be authenticated by the flight school/fbo where you did them, you just need a piece of paper with the hours signed by somebody. I kept a copy of all my 8710. After that you need to start a new brazilian logbook and copy all the hours on it.
I'm pretty sure that you can find different ways to do things by ANAC depending where you go, this is how it works in Rio.