I have heard horror stories about WalMart forgetting to tighten lug nuts after changing tires, and 20 years ago when I went to Monroe for a new muffler they told me they'd refuse to install it unless I replaced the entire exhaust including CAT, and when I went to Midas for new brake pads they told me they would refuse to install them unless I bought 4 new rotors and calipers. The dealership typically will do decent work, but they'll charge you double for parts and labor.

I look on the AAA website for AAA approved repair shops, then check yelp.com and BBB for reviews and complaints. Oil change is fairly simple, but if the oil filter or drain plug isn't properly tightened or they forget to screw on the filler cap you will lose that oil fairly quickly and that is really bad. Happens a lot at Jiffy Lube and WalMart, from what I've heard.