Replace Transmission Connector Adapter Plug O-rings Mercedes Benz 722.6

I am ordering the connector adaptor and O rings to change on E430. The car went into Limp mode. Wont go into gear at all on the auto or manual setting, the dash is not showing D 1, 2, 3. its blank.
Also ordered the OBD2 scanner.
On removing the adaptor will the oil drain out of that hole, so do I need to drain all the oil out first ?