When it's happening check your NATS light on the top of your dash near to the windscreen. If your immobiliser system works fine it will come on with ignition than goes out in few sec. If it's stays on with ignition than your NATS stopping you from starting it. If that's the case you need a Consult to read out fault codes.
The level sensor is attached to the N/S/R suspension arm and can be easily seen underneath. Basic adjustment possible at the lamps itself, but if there is any fault with the system or you replaced any parts on it, than it will need to initialize the sensor and you need Consult 3 for that (that's Nissan's OEM computer and only dealers and specialist like us got it). I hope this helps
Apart from the very early models the 370Z has a pollen-filter. (I believe it was introduced in end of 2009). Nissan recommend to replace it at every 18 month or 18k miles whichever sooner, but it still can be dirty ask them to show it to you the new one white and clan as it gets older it's turning black from the dust.
Nissan's Body Control System can be programmed for a few different function like Interior light time setting,wiper and door lock settings, but most of them very limited, not like German cars like BMW or Mercedes.
It is very difficult to reset these. You have to follow the procedure and pushing the rubber switch isn't easy either, sometimes it takes a few attempt from me too (and I done a few before ). Is the new motor genuine from Nissan ?
Take a close look on every pulley, I have seen it before when a pulley isn't parallel with the others it will rubbing on the side of the belt causing noise.
As I used to work in dealerships for the last 18 years I have to say unfortunately parts staffs has no training at all and I worked with people had no clue what's the difference between an oil filter and a bumper. It's not their fault, but being unhelpful and rude?! That's a different story...
Typical, that's what they do. Don't even mention their oil change called "full service". It's a shame on their network. (I do pads for £50 all in. Unfortunately you are too far ) I hope you get it sorted.
Personally I wouldn't pay that much for it as same quality kits are available for less, but top quality job well done and I have to say it's looks better than the OEM
It is quite common, you just didn't notice it before. As the oil moves around in the oil pan due to high g-forces (example in a long continuous high g turn) and it will slosh to one side of the pan away from the oil pick up causing short time oil starvation and oil pressure drop. It shouldn't cause any problem if it's only occasional and and it's not longer than a few sec. If you are doing frequent high g braking and cornering (like track days) than you should consider to fit a dry-sump system or a baffled oil pan. (A lots of different types/makes available for every budget.)
You only have to change parts if they badly worn or damaged, I had even changed just the disc before on my car as the pressure plate and the flywheel was ok. (Bear in mind the labour was free so it was worth the risk to save a lots of money. )
When you adjust a car all values should be the same (or at least are very close to each other) on both side, if it's not possible by adjustment than you have a problem should be investigated. If (as you said) one side is on +2 and the other side is on -2 than it's clearly an issue.