A question that I am not sure how to even ask...

If it was running ok before the oil change and the valve cover was not holding the engine oil , then a plugged oil return is not the issue . VDART may have the best possible daignosis , maybe you did fill the trans with engine oil . but really theres really not many places for 7 qts of oil to hide in any engine , i cant wait to hear th outcome of this one