Hello Dale,
I have a Denford MicroMill that I converted to Mach although mine's 4 or 5 yrs older than yours and probably has a little different controller. Mine has a 1996 SmartStep3 1/2 step 2A 40V control that still works well for what it is.
AFAIK all Denfords from back then use serial controls with proprietary software, dongles and such. I'll bet your controls are set up similar to mine and you'll find a serial sub-board plugged into the control itself. You jerk that puppy off and there's a 96 pin header (standard .100" spacing) under it that you can attach step/dir/gnd signal wires from a parallel port B.O.B. and go at it with Mach.
You'll be disappointed with the Sherline hardware as it's tiny, has tiny leadscrews (NO BALLSCREWS) tiny little brass leadscrew nuts and the machine itself is aluminum. Made for tiny little work and backlash is a constant issue. Sadly, nothing at all like your lathe. The spindle motor and KB speed control are pretty decent though.
The Denford enclosure and the electronics stuff is first rate. Go here:
http://www.denfordata.com/bb/viewforum.php?f=36 and after you learn what's where you can find everything you want to know incl. manuals, instructions on how to Mach/hack the control, etc. Great bunch of guys though you may have a little trouble with UK English?
Be glad to help if I can.
Milton