SImple answer, but the adapter plug from Crutchfield or someone like
Porsche Boxster Aftermarket Radio Installation Wiring Harness Antenna Adapter | eBay
or
2001 Porsche Boxster Stereo Installation at ****************************************
And wire the adapter to the plug that came with the Double DIN unit...couldn't be easier. If anyone wants one done , soldered and heat shrink send me your plugs and I will do it for a song....I'm still out of work
Dwight