How to replace the Brother DR3605 drum unit

When you receive a warning such as:
Drum !
Drum End Soon
Drum Ended
Drum Stop
No Drum Unit
Replace Drum
in any of these devices:
Brother HL-L5210DW
Brother HL-L5210DN
Brother HL-L6210DW
Brother HL-L6415DW
Brother HL-L6915DW
Brother MFC-L5710DW
Brother MFC-L5915DW
Brother MFC-L6720DW
Brother MFC-L6915DW
Purchase a new drum from and follow these instructions
Open the front cover.
Remove the toner cartridge and drum unit assembly.
Take the toner cartridge out of the drum unit.
Unpack the new drum unit.
Push the toner cartridge into the new drum unit.
Reinsert the toner cartridge and drum unit assembly.