PLEASE HELP

Make sure the batt is a, if the starter is clicking then you know it's getting power when you hit the key , probably the starter . Now that you've changed the ignition there's no telling what's wrong .

Since you replaced the ignition lock cylinder you now need to be towed to your local GM Dealer to have the new key programmed to the vehicle. The problem with the key not going back to the lock position so it can be removed is a common failure. Directly under the lock cylinder on the steering column is a hole. If nobody's ever been in there before it will have a cover on the hole. You pry the cover off and stick a small screwdriver or similar tool in the hole and push up. This will release the lock cylinder so you can turn it the rest of the way to remove the key. There's a solenoid in the steering column that sticks and causes the lock to get stuck. Sometimes the wiring in the console at the shifter is the problem. The wires ride back and forth with the shifter and over time break. This causes the solenoid in the steering column not to retract when you turn off the ignition key. So, at this point your local GM Dealer is your best bet. The security system has probably shut down the vehicle because it doesn't recognize the new key. Hope that helps! Jim