Factory fit AUX in doesn't give you any control it is simply an RCA lead (benefit being any mp3 player can be used)
Factory fit ipod specific connection is a dension
How the dension operates.
You turn on the radio and select cdc dension comes alive
You can control volume, skip tracks and i think skip playlists (skip playlists may be unavailable with the bluetooth fitted?)
Now you have 6 CD buttons for choosing which Dsc (playlist) you want to listen to, but only 5 of these will actually choose a playlist (assigned by alphabetical order so if you had a playlist called 1 Car Music it would probably work out as button 1 etc so you can designate which playlist goes to which button by naming your playlists appropriately.
button 6 lets you into the dension config where you can then select Access Ipod Gui or something similar where you can then control the ipod using it's click wheel, allowing a passenger to flick through tracks (i think at this point you can still use the steering wheel controls just fine)
Also if you press 6 and enter config you can use the track skip buttons on the wheel to select menu items and from that you can choose a play list (any that are on the ipod) or Album play which will play the album of the current track. Moving between menu's is slow and not a great idea to do while driving.
As far as I know.. no head units have aux in or aux out built into the headunits. I used a line level output converter (which the garage picks up using vag-com because it detect that something has changed in the stereo due to it being hooked into the can-bus system).
The white leons look great.. just give it a proper polish and wax before you let any dirt settle on it. Some people say the leons look better dirty, rallied look and all that
Anymore questions about ice>Link let me know, i can go to the car later and try something if there is anything you really need to know that I haven't explained or was unsure about.