The leak at the dipstick flange on the side of the engine oil pan is a well known issue with the 7.3 Powerstroke engine. The leak develops because the factory O-ring mounted inside the adapter swells over time due to exposure to oil. As the seal swells it actually deforms the inner piece of the adapter causing the outer nut to loosen. Some people will try tightening the nut to stop the leak and that can work temporarily, but it only deforms the inner piece more. The factory repair for this leak is to remove the pan and replace the whole unit from the inside of the pan. This is a time consuming and expensive repair.
This kit from 73dipstick.com reuses the internal part and moves the seal to the outside of the pan. Nothing left abandoned inside the pan and no welding, creating a permanent repair.