My thanks to those who responded with the info. For the sake of clarity, I wanted a way to replace the entire lot. I know the latest version of Samba will let me do the PDC/BDC stuff, but I didn't know how to replace the client workstations.
My thanks also to those who contacted me offline, especially the memory jog about how Solaris does it. I can look that up in my Solaris course material. (I'd forgotten about it).
I'll have a shufty at the info everyone's given me.
Again, many thanks.
Rod