Unless you buy a head unit with a stereo mini input jack, or one with a iPod interface, your options thereafter are pretty uncomfortable, clumsy and downright worthless in some cases.
I've ditched the iPod in the car, after one got stolen and a cop stopped me for inattention to driving (just a warning)
My advice, unless your going on a LONG trip, like weeks, just burn a bunch of cd's and get a visor holder etc.
Good thing about cd's, you get to play the 10-15 songs you want, in the row you want, when you want.
You also can write on the cd with LARGE easy to read letters so your not focusing too hard trying to read the tiny iPod type and wind up killing someone.
The iPod's "random" play is not right, it doesn't play songs equally often picking the same songs in a row the next day and again the next day.
One shouldn't have to make a complicated smart playlist to fix it and then it still doesn't work. It should randomize the playback equally and only when it has completed all the songs in the playlist should it reset, if it takes two days or a month, you shouldn't hear the same dam song three frigging days in a row.
Another thing, if your cd's get stolen they have little value to a thief because they are burned cd's, and even if they are stolen or ruined, you can burn more.
Any "iPod capable" integrated car system is going to cost a fortune, a lot of car makers want you to sign up for Sirus or something like that, so they don't offer a way to hook up a iPod.
I've tried the iPod and it worked with a cassette adapter on my old vehicle and on a 2 month cross country trip it was great as I had a huge playlist and we played the whole thing through. Of course cars don't come with tape decks anymore.
For shorter daily like trips the iPod is a royal pain in the arse, you always got to hide it. I don't recommned it in the car, don't waste your effort there.