If you are keen on using OEM parts and planning for a job that needs a lot of parts (or a handful of expensive parts), take a look at Amayama. They appear to be an overseas parts distributor that sources wholesale parts from various locations and packages them for shipping to retail customers. (They also turned up as a source for unique Japanese market parts in the thread on the Forest Air mod.)
Bottom line...I recently bought around 50 OEM parts for a whole bunch of maintenance on my M (coolant hoses, motor mounts, hood latch cables, new oil / transmission pans, gaskets, serpentine belts/pulleys, every drain/fill plug, dozens of OEM bolts, etc.) and it ran me around $1100 shipped. Pricing out the same parts from Infiniti Parts Deal (IPD) was over $2000. And walking up to a parts counter at the local Infiniti dealership and pricing this out would've required me to have a really good sense of humor.
I received all the parts carefully packaged in a custom box, and while I'm not a forensic analyst for counterfeit parts, every part looked and worked identical to the part I pulled off and all had proper OEM labelling. (I've also gotten Honda parts from them for my 2006 Odyssey and had similar success with genuine parts.)
Another data point - the huge K brace / butterfly brace for the front suspension on the AWD M/Q70 is prone to rotting out from rust. Parts in good shape run $450-600 from a salvage yard because they are in such high demand. IPD wants $700 + $75 shipping for new OEM. Amayama charges $250 + 100 shipping for the same part.
Note that pricing is dynamic, probably based on exchange rates and market + political trade conditions, and not all Nissan parts are available that IPD offers. But for big jobs that you can wait on it's definitely worth checking them out.
