Depends, probably, on the condition of the monitor and how much RAM you have. If the monitor is fading, then you'll end up spending some $ to get that fixed (they're pretty solid, though). If you've already added a bunch of RAM, the upgrade may be cheaper than buying a new machine.
Probably, though, given that the upgrade will cost some serious bucks, you'll be better off buying a native G3 or G4, or a later machine and upgrading that. YOu can get an all-in-one G3 from MacResq for about $800 (or maybe less) and then you still have a floppy and SCSI and you can add a USB or Firewire card when the time comes. Or you can get a refurb iMac for less than $500, but then you'll need adapters and external floppies and stuff for your legacy equipment. Consider all that stuff in the process, and you might end up on the good side if you upgrade. Sonnet makes a good product, and they'll work with you if you have trouble.
Good luck. Old machines ROCK.