I bought mine from Northshore, after getting an inspection by Envy Imports.
Would use Northshore again, wouldn't use Envy.
I also havent heard any issues about mirror rust, but if the car has a snow pack check for underbody rust. I notice Northshore always put pics up on their web site of the underside, which is great.
Grey import causes no issues with rego, but insurance depends. There are plenty of companies who will insure you (shannons, just cars, etc), but plenty who just dont do private imports.
Servicing is stupidly easy. Very, very simple to access the oil filter, drain plug, etc. i would do that myself if I was you. Cost you $20-$40 for a filter, depending on what you buy (Nissan, Nismo, Blitz or HKS), and then cost of oil, whatever your preference might be.
Shares a few parts with 350z or Xtrail, as well as the US Infiniti G35. You can get a lot cheap from Japan or from the US.
Great car, buy buy buy!