GMC Troubleshooting Questions? Ask a Mechanic for Answers
The freeze plugs are under the turbo and very hard to get to. There is an alternative option here, they sell a heater that goes on the oil pan. It has a heavy magnet to just slap it right under on the oil pan near the drain plug. You just run the electrical cord to the front and keep away from the exhaust. This will keep the oil nice and warm allowing for easy start application in the cold.
Let me know if you need anything else. I will do whatever I can to make sure you are totally satisfied.