It will all depend on the quality of your retro-fitter. There will be a lot of PLC work here that will not be part of your control. Are you getting a Centroid or Ajax control? Same company, Ajax is the lower end for cost and service.
I have not used Ajax, but I've done a lot of other controls. My favorite is Camsoft.
You can jump on Ajax without fear. I did it. It is a lot better than they (ajax people) say. I used to work with a Bostomatic vector 32 1995 that cost new $230.000.00, I would say with Ajax you can get the same performance with $4000.00
I got a centroid, very disastified. I would ONLY recommend the centroid in one case - If you are making parts for the iranian nuclear program.
On the surface, my centroid retrofit quote was about $4k less than a fanuc retrofit. Centroid screwed me out of $3k in options, and could use another $2k of spindle drive... So, I have trouble sleeping with this POS knowing a fanuc would have been cheaper and a thousand times better.
I just got my lagun mill up and running. I has new ball screws, with elrod machine brackets, and all Ajax controls and motors.
I had a few problems with the install. But with the Help of Ajax, she runs like a charm. I use this machine to digitize racing cylinder heads, and reproduce the machine work on raw castings.
The plc will be the biggest challenge for you, but Ajax will set you up.
I am very happy with my controls.
Thumbs up with Ajax!