I want in-dash MP3 and an aux input.

This seems like less work than other options since I can avail of the DIN cable for music and power signals for the amp. And the existing fader. I don't listen to the radio much so I'll get an antenna that doesn't have a mast. Leave it behind the dash somewhere.

It will be a lot of work to fit a 1492 or newer unit since the cables are all different. The 1432 has two 4-pin connectors, an antenna signal connector and an 8-pin DIN connector. The 1492 and newer units have the VW style connector that looks something like this -

http://www.discountcarstereo.com/images/pie/vw_8pin.jpg

Sixto
93 300SD