Just bought at GT, extended warranty?

So I just bought a 2008 G8 GT. It has 65k on it. I got it from a dealer who got it from the original owner who appeared to take care of it, but it has no real documented service history. I purchased an extended warranty for 2 years and 24k. The platinum coverage knowing that the car still has factory drive train coverage. I can still cancel it for a full refund. What do you guys think? Waste of money? It was $1800.