I've started on my xbox to micro atx case mod and was just wondering what the concerns with grounding are. I am screwing a piece of plexi into the atx mounts and then putting the xbox mobo mounts into the plexi. Do I need to somehow ground it?

the stand-offs will be enough, the motherboard actually gets it's ground from the power supply

The standoffs won't actually be touching the metal of the case though since they're going to placed into the plexi. But I think the with the atx psu it should be fine.