OP, sorry about the bad experience. This is one of the reasons I avoid letting other people work on my vehicles. Too many techs out there that don't give a [censored] about the quality of their work, too many shops that are trying to get cars in and out as fast as possible.
IMO, dealerships are generally the worst. You think they care if their negligence causes your car to break down/wear out years earlier than it should? As long as you don't notice, it benefits them since you'll have to buy another car earlier and maybe you'll buy another one from them.
There are some great shops out there and some excellent techs, but you almost have to know someone who knows someone, etc. I'm lucky, my brother is a tech and I've had friends over the years who worked at indy shops, so most of the stuff I can't do myself at least I can watch and shoot the bull with the guy wrenching on my truck, and 40 bucks under the table or a case of beer is all the payment owed.
I know wrenching on your own isn't for everyone, but if not, finding a trustworthy shop is critical. And I'm sorry if I offend someone here, but you don't need factory training to do an oil change. You just need to give a [censored]. You know, take pride in your work and do right by your customers. Funny that most people seem more concerned with finding a good barber/hairdresser than a good mechanic. [censored], you get to watch the whole time your hair is getting cut and if they screw up you're the first to know.
/rant over