Any ship's Engr IMTU would do routine maintenance and operation of the equipment, but that's comparable to 20th century fission-powered Navy ships. The reactor is sealed. Only a shipyard could work on it, generally by cutting the hull and pulling the reactor vessel.
It isn't quite that bad, but cold fusion Auxiliary would require "clean room" robotically assisted micro-welding for any internal repairs. Main power is hot fusion, and the core is not something you can work on by hand even after it cools down.
You could equip your Engr space with robotic manipulators and specialized equipment to work on the Main. It would add substantially to the cost of the PP and anything that damaged the PP would almost certainly damage the repair equipment.