Not being a Windows device makes it a bit harder but not impossible. The first step aside from messing with the ports would be to get hands on an update package (if any have been released, i dont have sync 3 yet). Regardless of the main OS system updates follow similar concepts system to system.
Reverse engineer an update package, provided there is no private key signing from Ford and you should be able to change the contents of the package with your own payload including possibly executable and scripts. Once you are able to get the system to run your own package its a matter of determining what kind of manifest you need to enable what you want.
The service ports on the unit are likely another point of entry though first it must be determined if they are actually USB ports or just using the USB connector out of convenience. Perhaps that has already been done?
Source : used to program robots, oil rigs and power plants. consumer grade systems are not much different though they are starting to include additional chips and digital signatures to prevent unauthorized access.
EDIT: Also the app platform is another possible vector, expect the apps to be sandboxed but no sandbox is perfect.
