2002 seville sts hid lights

Mr. Moderator,
I've checked many threads and can not find info on this subject..If there is, please point me to discussions on this...Thanks in advance..John

!.) Recently purchased 2002 Seville STS w/HID lights.
Previous owner placed standard halogen bulbs into car when ballasts
"burnt" out.
2.) What were the original ballasts installed as factory equipment?
There is two PHILLIPS 1653164-5 ballasts(XenTron- XLR135, XenDrive- XLD 135) still in vehicle(3 pin plug - 2 pin plug pigtails)

3.) Is it cheaper to replace entire system with aftermarket kits sold on the internet or replace parts from Cadillac. I'd like to have HID lights again but know nothing about them??

Again , thanks in advance for and information

John