If you want to stay stock, the best option in my opinion is to use a direct FM modulator. You won't be able to get this at Best Buy though, you will have to get from a car stereo place. What it is, is a box that plugs in-line to your stock stereo's antenna jack, it comes with RCA inputs, and requires a switched 12 volt source, and an on off switch. Many companies make these fairly cheaply, If you ask the stereo shop for an A/V input box, they will know. These are used a lot of times for TV in the headrest set ups. Install behind the factory stereo, add an RCA to stereo headphone jack cable - (less than ten bucks at radioshack), and put the ipod and the on off switch in the glovebox. All you have to do is set your radio to the correct channel and your good to go.
You should be able to do the whole thing for less than 50 bucks. While you are tapping a 12 volt source for the modulator, you could also add a charger for your Ipod to keep it going on long trips.
I did this in my f-150 and actually mounted a dock for the ipod in the dash tray, so I can see what is playing, and quickly change it at will.
