We need to replace the drum unit on a Min...

Not familiar with your model.... but...
When you install the toner cartridge, the toner is routed into a developer unit. this unit has "developer" in it that mixes with the toner. Generally you purchase the developer, remove the developer unit, remove the top cover of the unit, empty the contents of the unit. add the new deveoper to the unit, replace the cover, install the toner cartridge. a lot of times this requires going into service mode to reset the developer count and run a conditioning mode. Not sure if this is any help but here you go.