Honestly, it's a bicycle, not a nuclear reactor. Some people really depend on a shop for service, but if you own some basic hand tools, and you're generally a do-it-yourself-er, you can tune up a bike. Here are some good references:

http://www.parktool.com/blog/repair-help
http://sheldonbrown.com/articles.html
and for an old-fashioned print reference, http://www.amazon.com/Zinn-Art-Road-.../dp/1934030422

plus you can Google with "site:bikeforums.net" in the search field to find things on this site more efficiently than with the built-in search tool