The ballast isn't part of the bulb. The ballast is mounted to the bottom of the assembly outside the case and is a large aluminum cased device (mostly heat-sink) containing the high voltage circuitry that powers the bulb. The bulb does have some circuitry inside its base but definitely isn't the ballast. The ballast can actually be replaced without removing the headlight if you have a long flexible extension and a screwdriver tool and lie on the ground under the car. Loosening the foglight out of the way makes it easier to reach the front screw, but it can be done without doing so with the flexible extension. I changed one of my ballasts last month in this manner. There are only 3 torx screws holding them on in the 2006 model and the connection presses up into the headlight unit and makes the connection and seal. Any shop should be able to do it easily on a lift or with a floor jack without needing to remove the headlight assembly if you supply the part.
