Another easy way to piss off your mechanic is to come off with this line: "My friend, who knows about cars, told me this or that is the problem. How much does it cost to replace?"
If your friend knows so much, why isn't his ass doing the work? You know why? Because your friend doesn't know shit compared to me and you realize this. If your friend had 35 years in the business, he'd have his own place, not be working in some office pushing paper. Do me a favor, spare me his fucking comments because, odds are, he's wrong.
Auto repair is no longer the realm of the DIY guys on the weekend, 30 years ago, yeah, but now it's best left to professionals. No longer can you listen to a car run and diagnose it. A '71 Chevy, yeah, I can tell you what is wrong with it as it drives by at 40 mph. An '01 Chevy, I'd be lying to you if I said I could. In fact, if your late model car is running like shit, I'll refrain from making a diagnosis before I got a chance to see what the computer is seeing. Obvious (broken vacuum line or wire) is one thing, but if it's a failed sensor, I want to know exactly what it is before I waste your money throwing parts at a car. Hell, a low voltage condition (bad battery or alternator) can make the car's computer act real stupid, causing false problems. I could replace 2000 bucks worth of sensors and signal generators and still not fix the problem. Hell a broken ground wire can make the car run like everything in it is coming apart, if you don't know what to look for (there are about 20 ground locations throughout the average car), you can change parts all day and still not fix the problem. Even worse than spending your money like a convict in a whorehouse, is that the problem keeps coming back. My reputation depends on shit being fixed right the first time. We're too small a shop to have dissatisfied customers.
My point is that cars are complicated and Harry sends us to schools regularly to keep up with changing technology. He also spends tens of thousands of dollars on the best diagnostic equipment so we can do our work to the best of our abilities. I probably have as much time in a classroom as a Masters Degree candidate, does your friend? Tell him to work on his own car if he wants, but you're taking yours to someone who knows what he's doing. Me. It's a lot cheaper in the long run.
P.S. If you checked with your friend, because you realize that you know even less about cars than he does, to avoid getting ripped off, well as I said, I have 35 years in almost every part of this business, how are you or your friend going to know? As I always say, find a guy you can trust and stick with him. And trust him for Pete's sake. And regular maintenance and service is good insurance against catastrophic breakdowns. Off to the shop, have a good Little Friday!