I bought some 6K HIDs for my MKS last year and D3S is the correct bulb. Installing them is such a pain I put it off for a year and finally replaced them a while back. I had to take off the bumper to do it and that's not a lot of fun. Some folks here have done it w/o messing with the bumper but I don't know how. I have small hands and tried that first with no success lol.
I also replaced the fogs with 6K LEDs last year and they look/work great. Here's a shot with both sets installed.