hi hdokes,
I have played with 'prototrak' equiped lathe ( not sure of model) but only to fix minor connection problems in the control box (if i recall correctly, the pc part slides out one end of the box?)
From your description, it does sound like swi are geneating the video on the 68k board . If so, you may be stuck having to find a MDA compatible lcd (from where , i do not know) or some kind of adapter / converter. From (failing!) memory the frequencies are in the TV region, so there is some hope that one of the cheapo lcds will only need some sync signals adjusting to work.
Bill