Disassembling the iMac Alu

The website Amfiteatar published a step-by-step procedure to disassemble a 20" or 24" iMac Alu in order to change the HD.
If this operation is not complicated, one would need to remove the glass plate with suction pad, and later on it will be very difficult to install it back in front of the display without trapping some dusts! In addition, it voids the warranty...