I have a 1993 Mercury Villager. The stock halogen lights arent so bright so I would like to replace them with HID bulbs. I have seen 2 HID 9004 bulbs on ebay for 10 dollars. The seller has 99% rating. Then I also see the HID Conversion kits for my car. I am confused with this. Do i need the kit or could i just take out the old bulbs and replace them with the HID bulbs? What are the benefits to the whole kit Are these any drawbacks to installing just the bulbs and not the whole kit?