Can I change my radio to command in my 2005 e320
I would suggest a different route. I replaced the factory COMMAND in my SL 550 with a new Kenwood system. Kenwood (and others) sell great systems that include Satellite, HD Radio, GPS Navigation and Bluetooth and more. These systems are FAR cheaper than the MB factory system and have MUCH greater screen resolution and options. Additionally, dash kits specific to your car are available for all of these. When installed, they perfectly match and looks like they were original OEM. Conversion kits are also available in case you lose some of your steering wheel functions.
I have been researching this very same conversion. I was told because the MB in the 2003 E320 are fiber optic, I can not switch systems unless I want to replace everything including my speakers. Is there any truth to these statements?
No, the statements are not true. Whatever radio you decide to get, there should be an add-on module that will connect it to the MB fiber optic system. You will not need to replace or rewire your speakers. There will also be a module available, if you wish, that will retain most (maybe all) of your steering wheel functions. http://www.crutchfield.com/ is a good place for research. They may or may not have prices better than your local car audio dealer.
Looking for a Used E-Class in your area?
CarGurus has 23,232 nationwide E-Class listings starting at $1,600.
Search Mercedes-Benz E-Class Questions
Mercedes-Benz E-Class Experts