MPG Help

Can anyone tell me what is necessary to connect a MPG to a typical
Windows based controller. I'm in the process of rebuilding the DC
control circuits and panels on my mill and I would like to include the
MPG in one of the panels. The idea is to have a 3 button speed range
and 3 button axis select switches for the MPG. I have a Fanuc p/n A860-
0201-T001 MPG. I haven't got a particulur controller in mind yet. I
presume that somehow the encoder signal from the servo is disabled and
the signal replaced with the one from the MPG. Can someone point me to
a place on the web with schematics or maybe help me with this? Thanks
for your time!!