If you already have the Tiger re-installation media, dont pay to have it installed. There are many excellent sources on the web that have tutorials that you could print out and have handy, or you could view the tutorials on another computer nearby. Also many cities and towns have local computer clubs that meet up to exchange ideas and chat, some specifically apple. I would ask around. Many of these clubs are free, and the members help each other at no charge 🙂
If you dont own a Copy of Tiger, Craiglist or eBay might be your best bet. Just dont overpay. People like to charge exhorbitant amounts of money for older copies of OS X.