This ZF transmission is serviced, checked and filled like virtually all 5-6-8 spd ZF transmissions.
To check the fluid level you have the engine running temperature of the transmission fluid between 80-120F. Pull the fill plug. If the level is correct (vehicle on level ground or on a lift level) fluid should weep out.
To service the transmission meaning to drain and refill or replace the pan and refill you always open the fill plug first. Then remove the large plug with a large Allen wrench. It varies as to size but 16-18mm is in the typical range. If you have sufficient mileage to warrant a change in transmission filter verify the filter is an integral part of the pan or not. Typically the filter and pan are one unit and made of ABS plastic. If you do replace the pan/ filter note the low torque values of the bolts that are holding the pan on. They are usually in the 6-8 lbs-ft range.
To fill the transmission replace the drain plug and get a fluid pump at Harbor Freight or similar place which will allow you to pump the liter bottles of LifeGuard 8 back into the transmission pan. Fill until the fluid weeps out then install the plug. Start the engine and allow the transmission fluid to warm to between 80-120F. At that point keep the engine running in park and open the fill plug again. Fill until weeping and you are done.
It isn't that hard to do and anyone who believes in lifetime transmission fluid believes in the tooth fairy too. BMW and many other brands used to call out lifetime fill now they call out 100K miles between changes. ZF on the other hand has always stated that the transmission fluid should be changed at 50K miles.
You really have to search to find that information by the way but it is there.
No manufacturer wants to tell you to change your transmission fluid especially since LG8 isn't cheap every 50K miles. I will most certainly change mine then.
I have serviced countless ZF 4-5-6 speed transmissions and they are usually robust and reliable transmission built to handle a lot more torque that what is advertised.
Here is where I have been getting my supplies for ZF transmissions for years. They are the cheapest place I know of.
LifeGuard 8 Transmission Fluid
I don't see he has kits for the 8 spd yet but I am sure he will stock them of just order a pan/ filter from the dealer.
If you choose to change the fluid that is up to you but here is how it is done...
Hope that helps some...