Daytime Running Lights

I have been searching for the right bulbs to replace the daytime running light bulbs on my 07 clk550.  Problem is I think I am calling them the wrong thing and I don’t want to order the wrong thing.  I do want to use LED though.  I also am looking to replace the HID headlights.  There is nothing wrong with them, I bought the car from a guy back in November so I just want peace of mind that the bulbs are new.  ARe the headlights plug and play or is it more complicated than that?  Request assistance  Thanks in advance