you can always plug abs back in and zip tie it up and out of the way, light will go off
When my friend another rearend in his runner he had to unplug some relays because it was throwing codes to the computer and lighting up his check engine light. When he removed the relay/control box it quit throwing codes
What a lot of people do with the hole in the housing is measure it and go to a real parts store and get an engine freeze plug and put it in the hole. Marlin may sell them, but I would check the parts store so you do not have to pay shipping.