Adding a DVD? the only info I have on such is a company that will modify your system to accept DVD in the NAvI slot...HERE}
The DSP box can be removed and reinstalled on any 5er so equiped, but I don't think you can add it to a non DSP system. You really wouldn't want it anyway, I've heard of a lot folks removing it but no one wanting to add it.
The car should be pre-wired for cell phone, but most likely the compatible phones are outdated. I really don't know much about this though.