hello there carputer gurus..

just bought my first infill G4, received it today and i love it.. incredible how they put all that in such a little box..
but was consedering to buy either centrafuse or streetdeck to it.. see that the main thing on these forums seems to be SD.. but wich is better? i am very picky about navigation, i drive alot so need something good.. see that the sd uses map point from microsoft anyway, could i use any navigation software i wanted and "integrate" it into the g4? how does this work?
and how about the coolest thing, the OBDII feature, how is this done practically? is there an place to buy an obdII plug that plugs into the usb port or how is this done(dont laugh)..
i drive a 07 toyota vigo by the way..
thank you..