[SwissXC90]

Determine first where the noise is coming from: is it an open ended cable? Is it an earth loop? Is it a bad ground contact in the AUX connector? Is it a bad connection on the AUX loom connector? Or the DVD connector?

Does the noise happen when no connector is plugged in to the aux and no DVD is playing?
Does it happen When a DVD is playing? (put DVD into Pause mode to stop the audio, and just listen for the noise)
Find out when it happens, then you know where the noise will likely come from

If you want to replace parts blindly, do this:
Spray contact cleaner in the AUX socket and work it into the contacts
Spray contact cleaner into the AUX plug connector (you'll need to dismantle first) and mate the connector a few times
Unplug the DVD player and check if the sound changes
Unplug the AUX connector and see if the sound changes
Check for ground loops with Ohmmeter, connecting and disconnecting cable looms along the way
Check for cable loom abrasions especially on shields and grounds

Only once you have exhausted all the cable checks, have cleaned all the contacts, and sure that no ground loop exists, then start replacing parts. I suggest the AUX port first, as it suffers the most wear and tear.

noise problems are almost always ground issues: bad ground, no ground, or ground loop...