hey mate,
i had a similer problemin my r31 were my boot release would not work (wasn't the cable in the end but changed it any way).
you will need the following,
one boot release cable (u'rs broke right)
you will need to located were the cable runs, my was from the driver's seat up the side of the car in to the boot and followed around till the boot lock.
i did have to remove the rear seats and front seat to get under the carpet.
i then removed the cable its quite easy. then replaced the cable in the same way i pulled it out.
i then adjusted the boot lock (the bottom one) to get the boot to work properly and site right.
all up too about 1 hour in total.
should be fairly the same as the r31.
hope this helps