You would have to burn about 50 MP3 CDs and have them in your vehicle with about 140 songs on each CD. Either that or get a carputer, as I plan on getting soon. www.mp3car.com
Um ok or you could go a far easier route. I cant remember if that eclipse has the aux input built in, but if it doesnt they have an adapter you can buy to run through the changer input. After straiting that out I would just buy a 30 gig hard drive MP3 player and run it that way.