Hello:
This is probably such a basic question, I'm a bit embarrased to ask, but let me try:

I am a homeowner, and wish to install a GFI type outlet in an existing metal "switch" box
located in drywall/plasterboard. The box is the typical one used for either a wall switch or double outlet.
The GFI double outlet I bought in the hardware store leaves Very little room between the side terminal screws, and the metal box wall. Enough so that I'm concerned.
I understand that the plastic boxes are legal in my state, so I'm thinking of removing the metal box and installing the GFI in a plastic box. Good idea?
Comments?
I have also been wondering a bit more regarding plastic boxes in general, as I've never used any.
Mainly, what does one do with the ground wire
in the NM cable(not the neutral) when plastic boxes are used, and the switch or outlet does not have an additional (the usually green one) screw for it?

Much thanks,
Bob