From the work I have done one these so far it looks like it may be possible that rewiring the input will be all that is needed. I am in the middle of converting a Vanguard New Hermes 7000 and I have done a 3000 already.
They were normally run under the Gravograph software.
See the recent posts in this section.
I am running my 3000 machine on Mach3 software on a PC.
Old computers have a nasty habit of dying when the CMOS battery dies, you loose the info in your cmos, some of the batteries will also leak out corrosives that can attack parts of the motherboard rendering it useless.