e46 audio installation

Does anyone can help me with audio installation in my 330Xi. I have a car with harman/cardon sound system, with on-board monitor (so, BMW Professional), with TV-tuner and telephone, but without DSP and navigation system. My dealer told it is impossible to install DSP in my car, and what is more, it is impossible in general, but in the manual I have found, that the car CAN be equipped with DSP! So, if anyone knows, how to do so and which parts to order, any help will be appreciated. Also, I want to add DVD features to my system. I have TV tuner, and so I should have AV input. Where it is located? Thanks a lot...