Transmission oil change at manual transmission C70 II D3/D4/T5 not provided 🙁

Hello C70 II friends, today I wanted my C70 II D3 with manual transmission (as already mentioned in this post) to do good, and change the manual transmission oil. But far from it, it is impossible to reach the filling screw. You can see this wonderfully, but it sits press next to a carrier of the front axle. Reaching the filling screw is not possible with any tools, without first loosening the complete front axle or releasing the engine/gear and lifting it upwards In addition, it sits a little deeper in the housing, so that it can only be opened with one nut. A ring or fork key does not work. But even the 24 nut alone is already too long and does not fit between screw and front axle carrier. Is this to be grasped? Or do I make a fundamental mistake in thinking? The oil drain screw is beautifully accessible, no problem. However, the higher filling screw does not. On both, one recognizes the copper ring for sealing, they also look identical. I therefore rule out confusion. Obviously the transmission oil is filled in in the factory before installation and a change has not been planned at all during the inspections. Does anyone have a tip for me how to get the transmission oil changed anyway? Greetings Michael