Paul,
I’ve just fitted a new one, and the numbers I’ve been given are:
25hours after installation, then every 300hours or 12 monthly after that.

ATF (Automatic Transmission Fluid), is not 80W.
It is a specific product for automatic transmissions (it’s invariably red in colour).
There is a very long list of compatible ATF products in the ZF25 operating manual.
Others may have favourite brands, but you can use pretty much any fluid designated ATF for a modern vehicle auto transmission.
Any gas station will sell it.

Your ZF-25 takes 3 Litres, plus a bit more for the cooler, brake and lines.

Cheers
Dean

SY STELLA
AMEL 54#154