Purchased used 2000 DeVille in 2002 with extended after-market warranty. Car ran fine until minor oil leak in 2010 @ 85,000. Warranty company sited manufacturer defect, GM denied. Dealer convinced me to let them try to fix leak; they failed and said the engine could not be repaired and for me to tow it out of their facility or replace engine. I had new engine installed. Leak was minor and I should have just lived with it.
Have also lived with Check Engine Soon warning light for over two years. Changed both coils, mis-firing plug/boot, Crank Case Position Sensors, (both) three times but warning light keeps reappearing. Several knowledgeable Forum members have been responsive, but there are so many possible causes; I'm living with it. Otherwise good car, runs silent and comfortable. "Strongly" suggest Michelin Defender MXM4 SL, 245/50R/16 @ $130.20 + $30.00 from Mason @ Tire Rack!