In general, we really like our Brother printers (we have several). We did run into problems with this one with the "replace drum unit" message. It wouldn't go away even after replacing the drum unit with a new one. After looking at the manual and doing an internet search, we finally called Brother. Then we went though an hour's worth of troubleshooting before they gave us the way to reset the drum count.
To get to the reset menu that will let you reset the drum count, hit the stop/exit button. then the number 3 and 9 at the same time. This also gets you to the belt reset.
I like the brother printers, but the end of life for the consumables comes up way faster than they should. They need to let ME be the one to judge when the print quality is reduced to the point where things need to be replaced.