The only correct way to go with HID is to do a complete retrofit. That has been mentioned here many time by different members. A simple plug and play will give you better lighting but it will be impossible to properly focus the beam since the housing was not designed for HID bulbs. See page 2 of this thread;
LED Headlights Also, so-called HID kits are not DOT approved for on-road use and in many cases it is illegal to install HID in a non HID housing. The following was taken from a post in that same thread in the Performance Lighting Forum; "
The thing really worth noting is that it is against the law to put on an HID kit and stick HID bulbs into a housing that is designed for halogen bulbs."
I even contact one of the suppliers that members here have bought "kits" from and they admitted that the conversion kits were not DOT approved.
Peter