I recently did them on the SD.

The upper one is the real PITA. Get the end from the cooler unbolted and up in your hand. Then you must carefully swing the end going to the cooler in a big circle to get the oil filter housing end out from behind the motor mount. At one point, the cooler end it going to be pointed directly at the windshield. It's not easy, but, AFAIK, it should come out of the W123 in the same manner as the W126.

Now, going back in with the upper one is much harder. You can do it without removing the mount, but it requires quite a bit of patience to get the end of the tube to pass behind the mount. In fact, there will be a point where you are convinced that it cannot go. I recommend that you put a piece of duct tape on the end of the tube to prevent damage, because you are going to have to shove that tube fairly hard to get it to go behind the mount. Once the oil cooler end of the tube clears the mount, you are all set. The tube will just feed, in a circle, until the oil filter end reaches the oil filter housing.

But, you will spend at least one hour screwing around with that upper tube to get it past the engine mount.

This is why some members suggest removing the mount. I decided not to remove the mount but, spend most of the afternoon struggling with the upper tube. The lower tube is easy. Do it last. The upper tube needs all the space you can find.