Yeah... it's hard to just "throw these out"... More fun to upgrade them in every possible way, especially now when the upgrade parts that we used to drool over as being too expensive can be so cheaply obtained at a Goodwill computer store or other computer recycling store.... I mean, yes, they are dinosaurs, but dinosaurs are cool!
Years ago, I did the firmware upgrade on a slot-loading iMac that had been temporarily wrecked by a premature OS X installation. It involved jumpering certain connectors on the video cable and then hooking up to an external monitor looking for things on a severely disabled screen in order to open up the firmware package... Can't remember exactly what I did, or where one can find the info, but at least this gives an idea of what is involved...
If it's a slot loader, there may be the additional complication of an analog video part frying internally from the heat that was supposed to be convecting out of the machine...(sorry, it's been so long that I forgot the name of that part - oh heck.... google it!) That part has to be unsoldered from the analog video board, and the new one soldered in. Oh, and the massive, potentially fatal, stored up voltage from the cathode ray tube needs to discharged safely first before doing this.
Aieeee... so hard to get rid of one's pet dinosaur even when repairing it gets ridiculous!