the original motormounts are standard nema size so most motors will fit rightaway.I'm replacing mine with 2.0nm steppers wich is probably way overkill.
about the spindlemotor
The driver thats controling your spindle right now is just fine.It has a 110/220volts ac input(depending on your region)and a 180volts dc output.For rpmcontrol a simple potmeter can be used for manualcontrol.I guess mach and a likes should be able to be programmed to output the right signal to this driver.i haven't been able to find out what the correct signal is but i assume that it'll be around 0 to 12volts were the 0 is 400/min.rpm and 12v is 4000/maxrpm
these were all the instructions i received with the purchase of my own emco f1 i've have yet to find an occasion to start that project.
pls keep us posted and throw in lots o pics and i will try to be as helpfull as i can be.
Finally CHIPS you can have as much as you can without the doc. complainting about your cholesterol.