Much to my local Mercedes dealer's surprise, I keep on taking apart or adding to the electronics on any Mercedes vehicle I get my hands on. This strange hobby started when my dealer said it was impossible to retrofit TV or VCS/Linguatronic to my UK CLK (W208) some years ago. It believe it is always possible to retrofit items that were factory fitted to a car, even if not fitted for the country you live in. Of course, cost may be prohibitive!
Here are some documents I have written describing some of the upgrades I have done over time, and where to purchase the parts you will need from, and other information that maybee useful if you decide to embark on adding options to your Mercedes.
Where to buy the parts you need
COMAND-APS FAQ (NEW 19th April 2006)
COMAND and COMAND-APS Part Numbers (Updated 30th March 2006)
COMAND and COMAND-APS manual part numbers (Updated 30th Mar 2006)
COMAND Hidden Service & Diagnostic Menus (NEW 25th March 2006)
COMAND FAQ (Updated 25th Mar 2006)
Retrofitting COMAND (UPDATED 21st Feb 2006)
Installing and Upgrading Integrated Phone (including UHI) in European MY2002-2004 W163 ML (UPDATED - 19 Oct 2005)
Installing TV tuner in W208 RHD CLK
Installing Integrated Phone in W208 CLK
Adding Voice Control (VCS or Linguatronic) to W208 CLK
For information on Vehicle Diagnostics (and how Star Diagnosis configures the COMAND system) please see http://www.mercupgrades.com/autodiag
As you may have realised, I ended up buying a load of stuff that I never used in order to work out how to fit this stuff, and to find out which part codes are for the kits of parts that will save you substantial cash when fitting this yourself. Most of the spares will end up on ebay, but it still will have cost me a fair amount.