Nothing on the dash works

Oops you killed the BCM programming, now you will have to go to the dealer and have it re-flashed. Before main power is disconnected you need a memory saver tool plugged into the diagnostic port. Most parts stores carry them in stock.

Answer not posting

When you reconnected the battery, you likely blew at least one fuse. If other things in the car are also not working, it might be the mega fuse in the box under the hood; it's the big one that's bolted in. When you disconnect the battery, use a memory saver to maintain current to the battery and avoid blowing fuses and losing all the car's memory settings.