Just bought a E53 BMW X5 3.0d in Sterling Grey. Picking it up on Monday

Just a few Questions -
It doesn't have a SatNav/TV - can this be retrofitted? How much?
Or as a second plan - is it possible to just buy the screen from eBay an fit this in replacement of the cd headunit just so it works the radio via screen and nothing else? (No SatNav or TV)
Which are the best Running Boards to get, any decent aftermarket ones or are OEM ones the best?
Thanks. Ryan