I'm looking into swapping the CD6 in our 2008 Fusion with a factory Ford nav unit myself. If I have time next weekend, I may try to remove my Edge's nav unit (which also has Sirius) and install it in our Fusion.
Our Fusion has Sync and the voice command mirror, so that will also tell me if I can add voice commands by changing my Edge's mirror and right-side steering wheel buttons, and if I can add Sirius to the Fusion.
If I get this done, I'll let you know.
I
can tell you that if the 16-pin connector on the back of your factory HU has the following four wires, you should be wired to plug in the factory Sirius module:
Violet with Brown stripe (pin 9)
Yellow with Blue stripe (pin 10)
Green with Orange stripe (pin 1)
Blue with Brown stripe (pin 2)
Here's the pinout of that connector (C240B):
viewtopic.php?f=27&t=589
HTH!