Our house only has one GFCI and it's outside for the pool plug. I'm assuming the house was wired before GFCI became required. I have swapped out a GFCI for the mother in law, but that was just taking pictures, labeling, and reinstalling the same way. How hard is it to go from standard outlet to GFCI? I was reading the first one in the series on that circuit is the best place to put it. Would it hurt to add more to the circuit? How do you tell which one is first? I have swapped out all outlets and switches in our house a while ago, so they are all in good shape. The part that confuses me with GFCI are the terms load and line.

Here is my set up and what I was thinking:

We have a switch and plug in the one bathroom. I was going to just swap out plugs and think the two wires would go to the terminals without tape on them. Unless the switch is wired from that. I would have to look and see.

The other bathroom has two switches and one plug. I like the light up plug for the lights so when it's dark, you know which one it is. The outlet cover is hard to find for that set up at local places. I may buy one online or switch it to rocker type or push button type (same size as GFCI) and get a 3 GFCI cover.

If the bathroom plugs are on the same circuit, do both need to be swapped out? Would have to double check the circuit of course.

Deck has one in an enclosed plastic case on the siding and pretty much protected by the overhang. It is a couple inches above the deck. I believe that is the end of that circuit because it only has the two wires and ground. That should be straight forward if it just gets wired into the terminals without tape on them. Only issue may be making sure it fits into the box plate or may need a new one since I bet I tossed the extra parts.

Kitchen has a plug to behind the stove (not sure if it's on the same circuit), left of sink, right of sink, and under sink for garbage disposal (not sure of that circuit either). Should I put all 3 of those as GFCI or just one that gets power first?

Also, does AFCI do any good as I see some plugs advertised as AFCI/GFCI dual purpose. Can you wire a GFCI wrong, and if so will it work as a regular plug or not at all?

I am by no means an electrician, but have replaced plugs and switches before. I know black to brass and white to silver is the basic standard. I have watched many videos on it, but some just feel to me like they missed a few parts and don't feel 100% comfortable doing it.