Any bike shop does them, in fact they have different levels (basic to complete overhaul). Do your research, they can get pretty pricey. Most shops offer a free one with a bike purchase, that's what I am relying on until I learn a bit more about fine tuning a couple of them there gadgets.
For a long time Johnny Sprockets was my go-to place (I used to live right by there), although as I'm getting more comfortable tinkering with my bike I'm doing some things on my own. What are you looking to get done?
Correct me if I'm wrong, but a full tune up would include cleaning/regreasing any joints that need grease (headset, BB), running new shifter/brake cables/housing, truing wheels, cleaning/aligning derailleurs, and probably a good cleaning. (they probably clean it first.)
Running new cables and housing is easy to do on your own (if it's your first time, go to West Town Bikes on a Tuesday, prepare to be there for 2-3 hours and ask questions; 10 dollar sug. don.). Truing wheels is more of an art/science that takes practice and patience. But it's possible. Same suggestion: West Town Bikes (if it's your first time, allot one night for each). Aligning derailleurs, making them shift smoothly is maybe slightly less complicated, but you could do it with a little help.
Having it done by professionals is more convenient, but it's more expensive and you don't get any smarter. That being said, I love taking my bike to Rapid Transit in the Winter for the Winter Tune and just having them do everything. It's 150 bucks for the whole winter, but they'll do any labor whenever it needs it: you just pay for parts. It's nice to keep your bike clean and lubed in the winter.