thermo is the same for ALL RB motors
rb20,25,26,30
pcv valves are std on all modern cars, should be able to get a replacement from nissan direct, if not a generic one from a auto parts supplier
with the gromets, how many did you lose?
they are 2 piece, they have a steel washer within the rubber grommet, without the rubber part, there is a gap so it needs something
the rubber plug would be the half moon plug? i would be seeing nissan for that too