Ok the headrest monitors on eBay are missing parts and I have seen a few people tackle this job the hard way. All you need is a fm modulator, DVD player and a vizualogic a-2000 a/v modulator. You only need the monitors, so you can buy them for just $150 for the pair on ebay. The other parts sae is selling are useless with this set-up.

A-2000/Advantage A/V Box

Vizualogic Dual Headrest Monitor Package - Vizualogic's Dual Headrest Monitor Package