Good news and bad news.

Good news is with the oil pan removed (what a PAIN IN THE *** to remove!) I observed a small piece of gallery gasket material in the oil pan, at least confirming my suspicions.

Bad news is that means the gallery gaskets have gone, and I'm in for a very expensive repair job.

https://i.imgur.com/4IUUH4x.png

EDIT: Also after filtering the oil through a paper mesh coffee filter with a neodymium magnet, there was basically no metal contaminants. There was one very small piece of a silver coloured metal, but it was very, very small and the only thing present.

What is the preferred brand/supplier for replacement gasket sets?

What other items should I replace at the same time? Are some replacements "optional" ie: only replacing the timing chain if it is stretched, or am I better off replacing EVERYTHING?

EPS gasket set.

EPS Tuning Oil Gallery Gasket/Hardware Kit

With the number of miles you have on it. Water pump, thermostat, timing chains and guides.

Up grade the oil pump gears too.

https://www.z1motorsports.com/lubric...6c80dab2898b1b

Is the Z1 Motorsports option any good? https://www.z1motorsports.com/front-...t-p-17916.html

Z1 Motorsports appear to have more of the parts I need, meaning I can order everything from one place, rather than some from ESP and other parts from someone else?

I just experienced the exact same situation a few weeks ago. Installed a pressure gauge, noticed low pressure. I got a few quotes from local shops that wanted $1800-$2500 depending on the shop just for the labor. I ended up doing the job myself. If you don't feel confident about tackling it on your own than definitely pay a professional for it, it's not a small job. I used the Z1 gasket kit that you mentioned.

I've had a quote back from my local Nissan dealership and they sent through a huge parts list. Surely it doesn't require all of these?

Can someone help me figure out which of the below I need vs. don't need? I'm only wanting to replace the gallery gaskets, plus the water pump and thermostat, and then only the chain and tensioners if they are stretched/worn.

(keep in mind pricing is in my currency, not USD)

https://i.imgur.com/RRDtXmF.png

Someone's trying to line their pockets with that list and pricing. You likely won't need most of that stuff and $240 for a water pump is insane - don't let them bend you over like that.

Here's what I purchased from CZP for my gallery gasket job (ignore the PS cooler and ATI crank pulley). Got the gasket kit direct from EPS Tuning (see Rusty's link) and my mechanic sourced a new OEM thermostat for me.

Even doing the currency conversion, that's $160usd for a water pump. A new OEM water pump should be around $75usd or $110nz.

As far as what is necessary...a $60 set of gallery gaskets and some RVT. But, to everyone's point it would be a bad idea to have everything torn apart to replace those gaskets and not also replace the wear items while they are exposed. So what is necessary will be different based on the user. I would without a doubt replace the water pump and thermostat. If the chains, guides and tensioners look flawless I wouldn't judge someone for leaving them be if this was a weekend "I'm going to Starbucks" kind of car for you. If you plan to keep the car, drive it regularly or hard then yes. You should also replace the chains, tensioners, guides and oil pump gears. Those parts would run you about $1500nz. What was the labor quote, I don't see it included?

Ooops... duh :facepalm:

At 100K and planning to keep the car and drive it hard I probably should have done the chains, tensioners and guides. Everything was in good shape though so I didn't bother. I did put in some billet oil pump gears tho.

Labour quote is 6-10 hours at $166 NZD ($112 USD) per hour. This is for a Nissan dealership.

I think what I'll do is order the parts from Z1 Motorsports instead, so far I have this - is this everything?

https://i.imgur.com/7u1eQ3K.png

Except for the oil pump gears, that is exactly what I ordered.

How necessary is it to change the oil pump gears? From what I've read this means also changing the oil pump to new one, as new aftermarket gears shouldn't go in a used pump?

I only use my car as a daily driver with the odd weekend drive (no track days or crazy driving), so just don't know if it is worth spending so much on the oil pump/gears?

Final Update:

After presenting the quotes to the dealer I bought the car from for the repair work, they refused to accept there was a problem with the car, and when doing their own oil pressure test using a method different to the factory manual, they claimed the oil pressure was fine. They also didn't accept the gasket in the oil pan was a problem.

Fortunately they agreed to fully refund me, so I've now handed the car back.

Sadly for me, this is probably the end of the 370z train. I don't want to take a risk on another 370z that will have this gasket failure issue, and there are no 2014+ ones for sale near me.

You dodged a bullet. Now the dealer is going to sell it to someone else without fixing it I bet.