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You will need to remove the face on the new drive, as well as the tray face. After opening the iMac, you will need to remove the black thermal compound and reapply heatsink grease, which you can get from your local Radio Shack.
You will need a small phillips, a T15, and a T10.
BTW, lay the iMac face down such that the butt is facing you, and point the optical drive to your right. This is the easiest arrangement on all G4 iMacs.
Before removing the drive assembly, get the wires out of the little plastic C-clamp thingie at the bottom left.