taking oem player unit out / adding aftermarket one,question

[bosanci28]

i have my 2001 x5 4.4l sport package,
and i want to take the old radio/cassette out and add this here,
and i need to know if is there a plastic that will fit in there then to put the new unit in place,
also the wire plug from oem to the new unit?,maybe where i can find,,it..

and what about the wheel steering ,,the volume buttons ,,will they still work with the new unit?

let me now what options do i have

thank you so much