Welcome to the forum and to Zed ownership…
The norm is, that those with standard wheels or RAYS wheels go for the 20mm spacers, to bring out the wheel, so they sit flush with the arch, this changes the visual appearance too, making the wheels look as though they’re filling out the arches…
I offer the Eibach spacers in all sizes, 5mm, 10mm, 15mm and 20mm in the 350z fitment but as above, if you’re keeping the standard wheels then 20mm is the best option to go for…
As for the oil, have a quick search, there’s masses of info on this, we also have a few dedicated oil suppliers on the forum, who offer discounts to members, they’re always happy to help and advise too…