Back40 and others certainly have given you a lot of great advice.
If you're not afraid to get your hands a little dirty, do it yourself. Like he says, it gives you a chance to spot issues before you hear them or they get worse. You also know what you can depend on yourself for. Alternatively (and not a bad idea for those times when you don't have the time to change the oil before a trip), find someone you can trust to do it -but don't rely on a chain for consistency. I happen to use a Firestone place I know. I know the managers, I've watched their work, and they've given me plenty of reason to trust them when they could've done something easier and more profitable for themselves. Read PopMechanics or other sources for hints on oil changes (btw, many sources such as PM and online auto help sites will recommend prefilling the filter. Many argue it's not important, but it's easy, free, and can't hurt. -search the forum for a description.)
I am moving my daughter to Kansas next month for grad school, and she is buying her first car. I plan to go with her to a couple of local shops, as well as look around the dealership, to find someone she might trust. Among the questions I'll ask- a)tell me how you do an oil change? (I'm looking for prefill of the filter for bonus points, and selection of oil viscosity based on mfr's recommendation as a necessity. Checking dipstick after running the engine is also an important sign. -I don't use our Walmart because they slap a non-prefilled filter on, fill the crankcase, and send it out to the lot, without rechecking the dipstick after running the engine.); b) how often do you recommend an oil change -bonus points if they say to follow the mfr's severe duty recommendations and/or the oil svc reminder on the dash; c) what tire pressure do you use on passenger cars, minivans, and mid-size trucks -I'm looking for them to say that they fill to the pressure on the door placard, if they give me fixed numbers based on their "experience", this is a loss of points; d) how do you install the lugnuts when you reinstall or rotate tires? - Best is to tighten in cross pattern and use a torque wrench for final torque (though few do that),Acceptable is to use an impact wrench up to a torque well below the mfr's spec, then final torque with a torque wrench, unacceptable is to "Spin that sucka up w/ the impact wrench good and tight." Anyway, you get the idea.