What do you guys think of the timing chain stretching issue that is often reported on GM 6 cylinders? The 3.0 LF1, 3.6 LLT, etc. I have been looking at Buick LaCrosses to replace my Cadillac and this engine issue has been mentioned. Is it going to happen to most of these engines or will a good oil change history and low miles be enough to make the cars worth buying? Does the engine need to be removed at most shops for repairs or is it possible to replace the chains and guides with the engine in place? Thanks!