Hi Agro,
I had mine done as BobD did, full flush of the transmission, the oil is totally removed via the oil cooler outlet and replaced via the oil cooler inlet, around $800 (I had the steel sump replaced previously). The transmission was like new, so smooth and is still today after nearly 40K but I will have it done every 50K.
The ZF agent is Automac in Myaree

