A 1996 manual transmission originally specified 10W-30 or 10W-40 non-synthetic motor oil. This is in the Owner's Manual. If you don't have one, do a search online for a scanned version. It has lots of useful information. WIS should have that info as well.
Of course over the years the fluid may have been changed to ???.
The fluid Mimmi is suggesting will work. However you probably need to drain, fill, and drain. That is because we are not sure how well that fluid mixes with whatever the fluid in the transmission now. So that's quite a few euros.
I doubt it would hurt anything to use the motor oil like originally specified.
My apologies, it was 10W-30 or 10W-40, not 5W30 as I posted. That's been fixed.
According to bulletin I found in WIS, if changing to the new fluid, you are supposed to drain whatever is in there, put in 1 (ONE) litre of the new stuff, drive enough to let the oil splash around, and then drain and add the specified 1.8 litres. So you'd need 3 litres to do the proper job.
if the oil can be easily replaced i will flush and replace. if it will require disassemle of the gearbox i will leave it as is...
same for clutch cable: when i realized that you need to dismantle a lot of components just to lubricate it i gave up heheh.
p.s. yesterday i ordered a tech2 chinese clone for 250€....