Here is the part you need:
ACDELCO Part # 19151900
Very easy job. Study the photo above to see how it is connected into the radiator.
You really don't have to drain the coolant if your quick to pull out the old sensor and pop in the new one. You will lose a bit of coolant so be repaired to top it off and burp the system of air later.
1. Buy the part from local GM parts Department or Auto parts store or www.rockauto.com
wherever you chose.
2. Disconnect wiring connector. There is a Green connector lock. Just pop it out and don't lose it.
3. Stuff some old rags or paper towel below the sensor for spillage
4. Take out old sensor
5. Quickly install new sensor
6. Clean up (don't forget to remove paper towel or rag)
7. Top off fluid
8. Burp system
9. Reconnect wiring connector
No silicone needed. Just be careful to not damage the o-rings on the sensor.
If you need help just let us know.