Dont attempt to do this yourself, I did and I put about 16 hours of work into swapping them out (4 hours though were wasted the first day just figuring how to take things apart and where wires would have to be run. Only to run out of daylight and need to reassemble the car). The kit says plug and play, however it is not at all even remotely close to plug and play.
First you need to jack up the car and remove the wheels, then remove the front bumper and grill, then disconnect the wiring from the lights, then remove the lights from the car. Then you remove the back cap and disconnect the cable from the bulb, cut it off and leave the extra inside the light (it is impossible to remove completely without taking the entire light assembly apart). Then you need to drill into the back cap and push the new wiring through, and hopefully you have small fingers so you can reach inside through the cap and plug the new cable into the bulb. Next, cut the connectors off for the bulb end of the ballast, you will need to manually tie each wire into the bulb wiring. Also cut the connector off of the wiring that connects to the bulb itself. Use either wire nuts or crimp connectors to connect the bare wires from the bulb to the ballast. Then you need to run the wiring harness through the engine bay and connect it to the battery. Put the lights back on the car and connect the wires, use double sided tape and zip ties to mount the new ballasts somewhere. Or buy the full size ballasts and drill holes into the frame somewhere for the mounting brackets. Once you have all that done you can then put the bumper and tires back on.
If you attempt this, be sure and have a lot of alcohol on hand and ask a friend to help you. It will make things a lot easier because you wont be so pissed off at the amount of work you are having to do.
Now about the stock ballast, it is mounted to the bottom of the light assembly and can be removed. However, the cable from the ballast to the bulb is run through the inside of the housing AND attached to the housing. My friend and I tried for a full hour to figure out some way to get the wiring out so as to make use of that mounting location and the ability to run the new wires through. It just inst possible unless you completely disassemble the light assembly/housing.
And if you didnt know, our bulb sockets are D2S, so that costs an extra $15 from DDM kit.