I had the same problem with my column, I looked up the part number and ordered one from my mate at Nissan,but the problem is the parts book I believe is wrong as the top bush is not a seperate replaceable item but is bonded to the top nut.
I also tried to fit this new bush but one look and there was no way this would fit without severe hacking.
Take of your wheel and remove the circlip and using a small chissel and remove the slotted nut anti clockwise will show what I am saying.
cheers Ade