Or, rather spending $50-100 for a tune up, you could shell out a mere $15-25 for a good bicycle maintenance book, such as [1] or [2] or [3]. If you're less patient, a local REI carries [1] and [2]. This way you'll actually learn how to properly maintain and work on the bike yourself, which makes the whole thing much more enjoyable as you can tweak things any time, and after every ride if needed. Plus this saves tons of money; you'll be able to do 95% of repairs yourself and will only need to shell out money again if there is a very serious/difficult repair needing professional service and/or expensive tools.

[1] Zinn and the Art of Road Bike Maintenance, 3rd Ed.
http://www.amazon.com/Zinn-Art-Road-...1380953&sr=8-1

[2] Park Tools Big Blue Book of Bicycle Repair, 2nd Ed.
http://www.amazon.com/Park-Tool-BBB-...ref=pd_sim_b_2

[3] The Bicycling Guide to Complete Bicycle Maintenance and Repair
http://www.amazon.com/Bicycling-Comp...d_bxgy_b_img_b