I would say not all shops are shady, but I would say that some are, about 7 or 8 years ago my moms old explorer was overheating, dad put it in a shop, shop says it needs a new motor because of metal shavings in the coolant and wanted 8 grand to replace the engine, now as far as I know there is only one moving part in the cooling system, long story short, dad told them to replace the waterpump and thermostat and the thing ran perfect for another 20000 miles until the timing chain went bad, point is there are some shops that possibly aren't as truthful or knowledgable as they should be, however I believe there are some out there that aren't out to rob you either.