I got one of those Mickey Mouse DVD's off ebay for decoding radios,it states that the Nissan is fitted with a Blaupunkt radio but so were Mercedes and a whole lot of other cars and that the 10 digit part number was required as well as the serial number,however there was a general section and for that serial number the code showed as 0952.to put the code in,for the first digit use button 1 and then station +,second digit use button 2 and then station plus,third digit button 3 and station +,fourth digit button 4 and station +,check the code is correct and if so press station + to save it,raido should now come on,just try that code the once in case it is not correct,loads of places on line to get the code,I have used the one at the link below many times.
Jim http://www.radio-code.co.uk/nissan-radio-codes.html