thank your stars that you have a drain plug - american automatics have a sump but no drain plug in it, e.g. the FWD transmission of the chevy impala I have has a sump that is about 1 inch deep - the ATF stick reading is about 3 inches - so the level actually sits above the sump line.
try changing that out without getting bathed in ATF, (I do the cooler line method first and dont spill a drop of it).
anyway - proper cars (like MB) provide you a torque converter drain plug too - so when you drain the ATF from both places you have got about 90% of the ATF out.
In lower cost builds like all the other lineup - you are left helpless - you can do a cooler line ATF flush which will purge out all the ATF from the torque converter.