I got it. What the instructions don't say is that you have to also pry out the centre floor console to get to the 2 screws.
That was the easy part.
Next I went to a local car parts dealer to get wiring harness.
1 for Nissan 95 to 00
2 Pioneer to Nissan.
Neither harness was right.
Option then was to use existing harness for original radio and splice to the Pioneer harness that came with the new radio. Hmmm Challange was to find the wiring diagram for the original radio harness and match to specs for the new Pioneer harness.
So in the end I managed to nut it out.
All working fine.