easy.
buy an invertor from maplins, either plug the invertor into your cig lighter, or do what i did and hard wire the invertor into the dizzy blocks in the boot.
plug xbox into invertor. use xbox cable that has red,white and yellow rca outputs. plug yellow into screen, if your cd player had aux in, plug red and white into aux in (sound will play through stereo), if not, the red and white will go into screen aswell (sound will play through screen).
thats pretty much it.