Just replaced the O2 sensor with a brand new Bosch unit.
As expected, AFI didn't have a listing for an M35, but confirmed the Bosch p/n I gave them matched up with pre-'04 Z33 upstream sensors. The nissan plug had to be joined onto the wires from the new sensor, but other than that, it was very straightforward.
In fact, it only took 15 mins to change thanks to my shiny new O2 sensor removal tool!
(Craig & Scott, you've gotta invest in one of these things... Best $17 I've ever spent.) Lol
0258986602 is the bosch part number for the oxygen sensor in case you're interested.