HVAC Warranty Questions

If my new system should stop working, whom should I contact?
All properly licensed local heating/cooling contractors are certified to diagnose and repair any brand of equipment.
What happens if my new system does not work after installation?
Does the warranty include labor?
What if I need a warranty repair?
What is fastest possible way for me to get a defective part replaced from AC Direct?
I read that the warranty from Goodman is not valid for internet purchases. Is that true?