Finally I found some time to add aux in to my cd70 navi, fitted to a corsa c.
I will describe the big steps to do.
First of all, cd70 must be retrofitted with aux in parts. There is a pdf file on the web, modification guide aux in. I followed that one to solder all required smd components to the pcb. This required medium to advanced soldering skils.
Once this is done, unit must be upgraded to firmware 2007 or 2008. This will allow enable aux in by changing the code index for aux in. In general, if code index was 001, aux in must have 011, or another example, code index 003, with aux in enabled must be 013.
Car part. I removed the central console of the Corsa C. The idea was to fit the jackplug under the dash console, next to diagnosis plug. So is not in the eye view. I used wood drill of 8 mm. Also jackplug from conrad, the one with thread does not work, the dash plastic is too thick, so I used this one:
A bit of soldering and microphone cable, 3 original pins for the cd70 plug, mounted in the correct location and all is done. Sound is perfect.
Some pictures during installing, had to use mdi to clear canbus errors, had a cable with problems.