Sometimes you just know that someone is a hack. There is a specialist repairman who works only on one brand of cameras. He charges over 100 for a CLA or rather an "overhaul" and then admitted to me that this doesn't involve opening the shutter. I feel like I tell people this and they're so desensitized by bad techs that they don't get how bad that is.
To his credit he does adjust the speeds of electronic SLR's and clean and lube the advance mechanism in the top and bottom, but I find it very illegitimate that he would call it an "overhaul" and charge like 120 or something for it without opening the shutter. He was condescending to me in his very first response to my polite business inquiry and became actively hostile when I asked questions.
A repair tech should be frank about his or her limitations, but stand behind their work responsibly, and you should be able to tell that this will be the case up front. My current tech will tell you what he doesn't know, and the first tech I knew was retired from repair work and told me in no uncertain terms that she'd forgotten what she knew fifty and sixty years ago, but that she'd watch me open my camera and give me pointers if I wanted. Honesty and humility go a long way .. I would trust either of them with whatever they said said they were competent to do, because they represented themselves fairly and modesty.