I might not well be the first european to do this mod, but I would like to confirm that
YES, this mod does work on 2003-2005 euro spec HU
which as you know, do not have the XM radio/external cd-changer connector on the back of the HU, making most fancy ipod connection products such as USA SPEC's useless.
I followed this guide carefully:
http://my350z.com/forum/audio-video/93941-make-line-aux-your-2003-bose-headunit-step-step-guide-5.html
I had never soldered before, nor removed the dash. Overall, a normally skilled artisan as I am should take between 2 and 5 hours to complete the job.
I also modded the tape deck, removing an arm and spring, to avoid the need of a tape in the deck.
Sound quality is very good in my opinion, and using a normal jack, you can connect any type of mp3, ipod, car pc or whatever. I routed the wire under the gear knob and central tunnel to the armrest glove compartment, where my ipod is docked.
Downs are that you have to pick up the ipod to change song.
Ask for more details!