How much tranmission oil in a Megan Scenic Automatic?

Hi,
I have a problem with the automatic gearbox on an R reg Megan Scenic - it might be the gearbox on it's way out, but that will be really expensive so I want to rule out everything else if possible.
There seems to be a doubt about the level of the transmission fluid, but no dipstick or filler level, so I guess that means drain and replace it.
Does anyone know how much fluid it should take?

Thanks