ok
right dont go for fm modulator unless u REALLY have to,
what head unit do u have for 1,
as most companies do a little convertor lead, that has 2 phono imput leads on and u plug it in to the CD changer port on the back of your headunit, u can still use cd changer dont worry.
so what u would to is, stick tv video out, which is the lead u r showing, which is a s video lead, u would plug this in to the video in on the PS2, XBOX or dvd player, then on the PS2 for instance u would have a VID OUT, +2 sound out puts red and white phono leads, u would connect the audio cables in to the head unit adaptor which when the ps2 is powered on, the head unit would get a power serge from the audio and switch to AUX mode and give u sound through ur speakers.
u would need a power invertor for the ps2 or xbox, a 12v/240v invertor which u can get in maplins think they are like 30-40 quid.
worst comes to worst u would need an fm modulator, not the best things for sound quality in the world.
where did u get the screen ??