Transmission filler tube on 2006 Mercedes-Benz S350

Hello, the fill tube for the automatic transmission doesn't have a dipstick or a cap/cover. The oil change place tells me that it's not suppose to. This seems strange that a big gaping hole open to dirt/dust entering the transmission doesn't seem logical. Does anyone know about this? Thanks.

Asked by for the 2006 Mercedes-Benz S350
You probably won't find a professional mechanic at an oil change place, my personal opinion only. A Benz is an expensive investment and I wouldn't trust any quickie place to touch it if it were mine. Find a MBZ specialist to get you a dipstick for the trans.
If you want to find a specialist, here's a directory link for you:
I absolutely agree with Superbob. They probably don't even have the required fleece type oil filter and I'd be surprised if they even know what is the approved oil for your car.

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There should be a plastic dust cap on it. There is no dipstick. Unfortunately you need to take your car to a MB specialty shop to get the fluid level checked or serviced.
You are right about the contamination, so I'd stop by at a MB dealership and buy a dust cap ASAP, meanwhile just cover it with a plastic bag and some tape.