Oh poo! I didn't know it was a servo machine I thought it was steppers! You should definitely keep the servomotors and the encoders all you would need then are three servo drives and a breakout board. Don't forget a license for Mach 3 which for an educational institution is $100. You will also probably need an air spring to assist lift on the z access because Mach 3 doesn't trigger the break built into the servomotor.

I don't know which servodrive's to recommend because I've never replaced servodrive's before. However, I have contemplated replacing the techno electronics on my own machine quite a bit.