Could it be that she got a Non-HGT model? As far as I know only the HGT has the navi system.

The DIN slot you are talking about, is it at the very top of the dash? That's where the headunit plus navi is located in the HGT with the cd changer right down the bottom of the dash.
This would be the place for the empeg, if the gear lever doesn't block access to this slot...

Thanks for the tip about the connectors! At least this doesnt seem to be a problem, after all.

Marc