1. Remove any encapsulation pans on the car. Important.
2. Park it on a level surface.
3. Put cardboard under the car, TAPING it to the floor.
Now, here's the tough part. If you fit under the car, slide under with flashlight and see if you can locate the leak. If not, you can jack the car up, and USE STANDS (Never get under a jacked car) and use a light. Look for a trail, not just a drip spot.
Now I know you said you don't have jack stands, but maybe borrow them?
As to ATF running clear, if often picks up dirt as it leaks down, so don't be fooled by a little colour change.
Gear shifter-area leak could be tranny fluid, and your small leak would be difficult to detect on the dipstick. But, if your pan is in place, it might be engine oil that has rolled back along the pan and leaked out at the back. Depends on how far the pan goes back. (I don't know on that car...)
I had a friend that kept misdiagnosing hios front main seal leak thanks to MB's belly pan.
When the dealer diagnoses it, ask them to show you.
1998 C230 "Black Betty"