What is the actual shop time needed to diagnose a bad LCM?

For diagnostics there really isn't a book time, it all comes down to the methods used and what else they test along the way as well as what the symptoms were from the start. It's a lot like going to the doctor saying I have chest pains, some will send you for a scan, others will draw blood and look for specific chemicals in it, still others may do all the above as well as have a stress test done. Then you will find the doctor who sets down and asks about the pain, what you did before the pain, what you ate and if you did anything out of the ordinary, who then wants very specific tests before telling you that you had a minor heart attack and administers the correct drugs. All take different times. Same with auto diag and the approach used.