Laser Printer question...

[Gaming Computer]

Careful with ripping apart waste toner containers. Its often messy and toner is carcinogenic.

Alot of manufactures refer to the drum as the imaging unit, off the top of my head Xerox do. What you are probably receiving is a prompt to replace the drum. Manufactures recomend you do this over time/number of prints to firstly stop a decrease in quality and importantly for them, make more money

Keep printing until the print fades then look into it.

When you do look into it, here is the manual: (edit cant post URLS)
Hope this helps

[watercooled]

If you can get a look at the drum you should be able to get an idea of what sort of condition it's in - new ones normally look shiny and smooth, worn ones look dull and have visual imperfections. It's not perfect since some age better than others but like I said it should give you an idea. And as Gaming Computer said be very careful with toner it's very messy and you really don't want to breathe it in! If you ever manage to get toner on something, including your hands, use plenty of COLD water to wash it off - hot water can/will fuse the toner particles to whatever it's on and it's likely to permanently stain it.