P0008 is caused by a worn stretched timing chains. Timing chain replacement is not a reason to replace the engine. You may also have misfire codes, rattle noise on cold starts and other codes. The dealer has the know how as this is a normal repair for the 3.6L.
Good thing is the Lacrosse dose not need the engine removed to do this job.
Note: Poor oil change maintenance speeds up the ware on the chains
