It is pretty simple, just time consuming.

Get the headunit...

Connect the yellow wire to a constant power wire (existing constant power or battery)
Connect the red wire to a switch power wire (ignition)
Connect the black wire to the chassis of the vehicle
Connect the White (L)/Gray (R) wires to the front speakers
Connect the Green (L)/Purple (R) wires to the back speakers
Get a window antenna to connect to the headunit for the radio channels.

Time consuming part is running the wires and cutting the location of the products if stock fittings do not exist.