My first 10k service

Just bought a 2016 10k old GRiSO and want to do service of fluids and eventually grease everything but I’m a bit confused about a few things . As you can see I’m in Australia and have a contact at Repco. I’m thinking Penrite products ( upon reading Pete’s recommendations.)

1 , gearbox and diff 75W90 but semi or full synthetic - does it matter?

2 , fork oil, in the manual it looks like 5w - 20w. I’m after a plusher ride so I’m thinking more towards the lighter end - any comments please
   And what is the story with levels, measured from top or quantity?

Thanks

What gear oil you use in the 75/90 range doesn't really matter but we always use a full synthetic from Penrite called 'Pro Gear'. Less than a litre will go both gearbox and bevelbox.

Forks? Definitely go 5wt. They're massively over damped.

Do the swingarm bearings and shock linkage bearings now or pay a lot of money later.

the forks definitely benefit from thinner oil
I've found that it's wise to reference the fork oil viscosity index when choosing an alternate  brand & weight as it seems the manufacturers oil "weight" can be somewhat subjective. the chart will let you compare all of the brands and weights

I tried to attach it, but the site won't let me attach a pdf for some reason. you should be able to google it