I am building my own computer, and I am having a problem installing the motherboard to the case. I have a few questions:-

1) There is a metal standoff on the case that doesn't fit my motherboard, will that short against the back of the mobo? Do you have to insulate it to stop it touching the back of the pcb?
2) Around the holes on the mobo there is a ring of metal, is this seperated from the tracks on the mobo? Is it ok for the metal screws to touch this ring?
3) How many standoffs is adequate to support the mobo, because I cant see a way of putting one in each corner.
4) There are 4 holes near each corner of the cpu, and I have 4 plastic inserts that seem to fit those holes, would they go there?

The motherboard I am using is a Gigabyte GA-7VRXP

Cheers in advance.