Thanks everyone, I think I have a place to start.

I've started looking at as much as I can of the broken original disk with Fedit to see what's going on there... Norton Disk Editor seems to let me see the boot blocks but not edit them, maybe I'm missing something there. The tour application is in a different folder, so not sure about tricking the system into thinking it's the Finder unless I just do away with the folders entirely. I'll keep on poking at it.