Radio code required for Focus 5000RDS please

[zrx1100]

Just wondered if anyone knew of a possible code or how to get one for the above radio, had the car for 6 years with the original battery and guess what it has gone and the prev owner has not written the radio code anywhere so I am stuck now with 'CODE ?' on it. If I have to take out the radio to look at the serial code how do I do that too, is there a special tool required? Thanks in advance.