iMac g3 slot loader. dead screen. how to wipe HDD

If your iMac has a slot-loading optical drive as you've indicated, it must be a 350 MHz processor model or faster. The tray-loading iMacs 233, 266, and 333 MHz are different than the slot-loaders in terms of hard drive removal. With a dead screen, you might as well just remove the hard drive if you're concerned about data on it. That way, you can e-cycle the rest of the computer and do what you wish with the HDD. There are YouTube videos that show the disassembly procedure and hard drive removal does not expose you to any shock hazard. This step-by-step disassembly procedure shows the carrier in which the hard drive is mounted and how to remove it (Steps 11 & 12).

The iMacs used IDE hard drives. If you wanted to retrieve files, there are generic adapters sold in PC stores that plug into the 40-pin IDE interface and convert it to a USB connection. I paid about $15 for the one I bought. You could reformat (slow format is better) the drive in a Mac or PC and once wiped, do whatever you wish with it. If you have an assortment of screwdriver tips including Torx sizes, you could remove the top cover from the drive and extract the platter inside.