Hi and welcome to the forum
The oil pressure gauge will vary with the revs and temperature so expect to see variations between 20 and 80.
Nissan recommend fully synth 5W30 engine oil.
The shift light can be set at what ever you want, however 5000 would be a good starting point, remember it is not a cut.
I stock all the service stuff required for P1 - P2 - and P3 + much more.
Have a look in my 7 page sub forum for more goodies
viewforum.php?f=157
If you require some help in what is required for your P3 then just drop me a pm or post up here.
Alex.