That sounds right. Make sure the screw that you chose is indeed a ground. The green wire you grounded was the light green wire from the HU?
One way to troubleshoot this is to disconnect the SWIPS and the HU and reconnect the battery. I would leave the GMRVD disconnected while doing this because you don't have to have it. Turn on acc power with your key and see if any thing gets hot. If it does, recheck all your OS4 wiring. Call PAC if you can't figure it out, they seem to be pretty good about helping. You might want to call them anyway to see they think the OS4 is damaged.
Disconnect the battery connect the HU cables, reconnect the battery turn it on a see if anything gets hot. If it does there is something wrong in that part of the wiring.
Then, reconnect the SWIPS (after taking the battery loose) and try again.
If that all works, reconnect the GMRVD and check again.
You don't have to reconnect the battery each time and some people don't, but why risk it at this point. I know you are probably very frustrated right now but it is not the time to push your luck. Be methodical in troubleshooting and recheck all your wiring connections. Make sure everything is well insulated when you made up your harnesses.
Make sure any wires you did not use are taped up so that they do not short anywhere.
Let us know as you progress. What part of GA are you in?