The NTG1 in my 2005 R171 has both factory fitted CD-changer and Aux input. Both are in the glovebox. The aux-in socket is on the far left of the inside of the glovebox (RHD car). If you don't have that (on the far right for a LHD car), then perhaps someone else with more knowledge of US-spec cars will be along shortly to answer instead.. 