ccfj1 is mostly correct.

You can keep the same nav computer - but you must re-program it into colour mode.

You must fit a new On-Board-Monitor (display) and Radio Module (radio) with associated mounting brackets. Your heater controls need to be relocated to the space below where they are. A new trim piece is required.

You must fit a retrofit wiring loom (easiest) or make your own wiring loom (hardest) to carry the video signals from nav to display, to connect audio signals from tape or CD to radio, to extend the speaker/audio cables from the current headunit location to the radio module (boot), and to extend/change the antenna cable from headunit to radio module, and to extend the CD changer cable. The retrofit-loom is by far the easiest to use.