cheap video integration?

I own a (european) Prius II from 2007, and I would like to attach a carPC. Video is enough (for now) and I dont need touch feedback. I just want to see the image of the pc. I found several threads here, but they eiterh are quite old or talk about expensive mods.

My car has no navigation system and no rear camera. So there is nothing where I could just hack in. But... I read that the simple Prius II uses two video interfaces. One RGBS interface that the prius computer uses to output the image, and the gvif that normaly the nav would use. My pc would output a composite signal. Wouldnt it be possible to simply detach the prius computer from the display and attach mine? I know that in this case the touchscreen would be useless and I would see the information from the car. But would this be possible?
thx.