A 3 year old, i-Mac G5 core i3 machine with a dirty screen. The usual has happened, dirty smudges behind the glass plate ! I live in a small apartment and the mac is, unfortunately, close to my kitchenette. The little cooking that I do seems to have created some 'Smoke' and/or 'grease' smudges behind the glass plate.
Had no trouble removing the Glass plate with the suction cups that I already have, cleaned all (Screen and Glass Plate) with 'Apple' i-clear, repalced my Hard drive with a larger unit, 1 GB, and cleaned up the dirt accumulated inside.
Setup the unit properly by lying it down on a blanket on my bed, grounded myself and the unit before opening, took notes as to the placement of the video and drive cables before removing, made sure I had plenty of time and all the right tools !