1. Don't know or care. Sorry.
2. Both. The data uses the included GPS map data, but also downloads images from Microsoft Live Local (or whatevever they're callying it this week). You need some sort of internet connection. It doesn't need to be WiFi. It could be tethered to a cellphone data connection or a wired 'net connection.
5. Yes, but I wouldn't expect perfdormance from the G4 unit. There may also be driver incompatibilitied.
Why do you think you want Vista in the car anyway?
6. Yes, but you void your warranty by doing so.
7. See #6.