Best retrofit for less?

I am planning on pulling a dead Bandit control off my shizouka knee
mill. The servo's are still in good working condition. What route
would be best to drive them and interface between the computer? I
don't know if I wanna keep my servos or use steppers with quad
encoders. The current rating on my servo's is 500in/oz. I'd like
this cost less than 1000 but somehow is seems like wishing in one
hand and shitting in the other. Please if unclear ask me questions,
otherwise I value your advice.