Does the 2003 Clk 430 require the Navigation Option to have the Command
System? Is the Nav system on the 2003 functional? I read in other posts that it can not be updated. I am ready to buy a 2003 CLK 430, Thank you

 

COMAND is navigation so I don't know what you're asking here.

Yes, it's functional.

Yes, it can be updated using DX Navteq CDs.

 

What aftermarket navigation unit will provide turn by turn display in the instrument cluster. How difficult would the installation be. I am new to this forum and I am trying to decide between 2 CLK430 Cabs; one with Nav the other without. Thanks for your patience.

 

No aftermarket NAV will talk to the OE TFT in the dash.