Installing a rocker switch. What's the size of the cutout on the dash?

Have an 04 Tacoma. I was going to run a 12guage power wire from my battery to the dome light on my shell but i got to thinking maybe I should install a lighted switch inside the cab so I would be certain I didn't accidently leave the dome light on.

My question is, what's the size of the panel cutouts next to the outlet plugs. I'm seeing rocker switches with sizes from .830" X 1.45" to [COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20].550" X 1.125". Don't want to buy the wrong size.[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR]

[COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20]Should I be getting a 2 prong or 3 prong switch. Do I really need to ground the switch if I'm going be grounding the shell anyways? Might use this wire and switch for something else in the future like for an inverter or something.[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR]

[COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20][FONT=Helvetica][SIZE=1][COLOR=#231f20]Also what size I fuse should I be using. I have a 3amp fuse laying around and the dome light is 1amp. Would this be ok? (I've forgotten everything from the electrical class I took long ago). I might add another dome light or two in the future.[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR]