Can anybody offer any information about upgrading to the satnav command unit. Will a unit out of a clk replace the standard radio unit in my clc 180 k, I have managed to locate a unit at a Mercedes breakers in full working order, however, there seems to be an extra unit to be fitted in the boot. What is this unit? Is it an amplifier for the sound system. Not actually viewed this unit, yet just going off what I have been told, I know it will need a separate GPS antenna but would be grateful for any info as to whether the plugs will fit etc or if indeed this is a viable conversion.