well, you've got two choices if you don't feel up to removing the new boltless style dashes yourself.
The cheapest and easiest option would be to take a personal cd player and use a cassette or FM adapter out of the _*LINE OUT*_ jack. (yes, I know it does work out of the headphone jack, but it is too easy to send too "hot" (powerful) a signal to your sensitive tape deck) Cassette adapters are available at most any department store or place that offers personal or car audio, and run $10-20. FM adapters are available at most, but not all of those same places (you can usually find both at Wal*Mart or Target) for about $20-30.
Your other option, if you insist on having a built-in cd player will run anywhere from $120 for a cheap, basic cd/AM/FM, to $400+ for a combo cd/cassette radio (the bottom end of combo players are almost always equal to or better than today's stock head units), to a minimum of $400-600 for a cd changer, which you may have to get a new head unit (radio) for, anyway. (If you get a particularly high-powered head unit, you may have to upgrade your speakers as well, to avoid blowing them)
There are a number of different places to take your car, once you have chosen your equipment (a favorite vendor of mine is Crutchfield www.crutchfield.com
). Many electronic chain stores such as Best Buy and Circuit City will professionally install these for you, even if you don't buy the equipment from them. These major name retailers will do the job professionally and offer various warantees on the services. Just the installation at a store like that will run from about $50 for just a radio to $200-400 for a complete system design for your car and installation, including head unit, speakers, amp, and subwoofers. There may also be some local independent car audio custom shops in your area. These places usually deal in higher end products, and this would be where most of the serious "bass-heads" go to have their big car systems worked on. Prices and quality both vary greatly, depending on the individual shop, so if you want to go this route, then I would suggest asking around of people you know who have high-end audio systems in their cars, and see who they suggest.