I was a GM employee, and the only thing that they offered was always finding ways to rook me on warrenty work.
Trust me, GM ain't doin' anything specail for its employees, and the only advantage that GM employees have acess to part numbers, whereby someone in parts wouldn't feel like dinking around with finding such information for someone off the street.
I did have one edge, but it wasn't on spcail parts. I don't know whether it was because I was a GM employee, or if it was a perk offered by the dealerhsip. I could buy parts for 10% above what my dealership bought parts from GM. By the way, I could only buy parts for my cars and my necular family.