Not necessarily. The logic boards for the G3 iMacs are different. The original 1998 model has a different shaped and pinout logic board compared to the 2000 or late 2001 models. The tray-loading models 1998 through late 1999 (which are Rev. A through Rev. D) not only had their CD-ROMs as a tray-loading drive, but the logic boards as well, were fitted inside a tray-like metal/plastic cage. To access the logic board, you simply undo a few screws, pry apart some plastic panels, unplug 2 cables and pull the assembly out.
The next generation of G3 iMac models had the logic boards screwed in underneath the high voltage and CRT assembly. A little more screws and panels to take off before you can gain access to the logic board. Usually these models had CPU speeds starting at 350 Mhz through 700 Mhz and their CD-ROMs (some with DVD-ROMs and Combo Drives; CD-RW and DVD-ROM) were of the slot-loading nature (Instead of a tray that pops out when you eject the disc, you had a slot that you fed the disc into. The drive's mechanism will automatically pull the disc in and eject it out for you.)
Although swapping out RAM is a good suggestion, be careful you match the right type of memory sticks with your iMac. The Rev. A through D G3 iMacs used sticks of memory similar to that found in a laptop computer and were rated as PC-66 or PC-100 standard. You will have to pull out the logic board cage assembly in order to change out the RAM on these models. The 350 Mhz through 700 Mhz G3 iMac models all used desktop memory of PC-66, PC-100 and PC-133 standards. For these models, you only have to unlock a door underneath the case and pull it open to get to the RAM; it's that easy.
You can run your iMac without a PRAM battery, but in some cases, running without a battery will also present the same symptoms of the problem you've been having. I would only run without a battery if I knew that the cell was dead.
73s de Phreakout. :rambo: