You didn't get one of those hybrid Z06's did you?
Hopefully you can get this wrapped up so your baby can be back to normal. It must be frustrating. Most likely a blip in the programming as MM stated. As long as this is limited to the instrument cluster, you should be fine to drive your car. All the sensors are working by evidence of your HUD providing you with all the information. You're HUD will let you know if anything is wrong. The gauges in your IC just read what is happening, the car/computer doesn't use the gauges to determine if everything is operating within parameters.... However, maybe you could use this opportunity to take the car for a good rip and when the cops pull you over, point to your blank dash showing that you couldn't know what speed you were going!
Keep us updated!