The parts for a full AMI retrofit are very expensive, something I was considering before I saw the price.
Roughly between £700-£800, believe me I have asked installers.
Also if u don't have a CD changer in the glovebox, that another (almost) £300.
An other option u have for iOS devices (and works for mk1 &mk2 RNSE) is the Alpine KCE-425i, shows track info in the head unit screen, but u will need the video in motion hack or kufatec module to use this whilst driving. All in circa £350
The final option is a Denison Gateway module, which gives u track info on the little screen (DIS) between the clocks. Some models also come with a USB socket. Price is a bit cheaper than the Alpine.
You could obviously save a few £££ retrofitting yourself if u are competent with auto electrics, but I would think the AMI install needs a professional and needs to be coded in with VCDS.
I've resigned myself to using SD cards for music. Up to 4gb x 2(non SDHC) for the mk1 and up to 32gb x2 for the mk2.