i am trying to install a factory nav unit out of a 06 c55 into my 05 c230 what do i do for an antenna thanks

Search this has been mentioned way to many times.

Yup...Search The Forum.

Or - You can get an OEM WIS disc and it will tell you step by step what and how to do it...and you can print all of the pages out to bring to the shop!

But...Until you search...You need to...

1.) Locate an antenna - OEM, OEM with union or aftermarket >.45" thick with a BLUE Fakra end - OEM is bent down 90 degrees.
2.) Pull out instrument cluster and cluster hood
3.) Remove three t20 (or t25) screws from instrument panel frame
4.) Place antenna above instrument panel frame on top right (inboard)
5.) Run antenna cable to back of COMAND through center console center stack

STF, and good luck - Enjoy COMAND...you may need MOST Fiber Ring configuration - and will need STAR DAS to enable turn by turn in MFD.

where do i get antenna from dealer or aftermarket thanks

ebay