Hi Ironnike,
I believe that unit is from a CLK being part number 209, so it wont actualy fit!
As your car is pre-facelift you will need a Comand 2.0 unit, as that's a plug and play option, otherwise an extensive loom retrofit is required! i don't know how hard it would be but maybe an NTG2.5 retrofit would be a better solution as it is the most up to date option, with loads of extras you can do with it, but it is costly, so its all down to what you want to spend.
I would suggest contacting Comand Online, they helped me with my upgrade and it went flawlessly!
Hope this helps!