Al is not here, and I cannot reach him, I will answer what I can
I watched him replace, was NOT hard, it is akin to replacing any wall plug, with the reminder to watch that wiring, I think it is a bit different to make it a GFI. Did not take him long at all, minutes.
He bought at a Sears or Lowe's or Home Depot or something, NOT a RV place.
Last question, not sure. I think it would, if the main one is popping out that little red indicator, then the rest of the plugs on that line will NOT work. If you fix the main one, the others should work, IF that was the REAL problem. That is how it works in my stick built. IF the GFI pops, nothing else that is wired in that line will work till I get the GFI functioning again.
Disclaimer, I am NOT the electrician, only married to him!
Sorry bout your weekend!
Carol