I co-owned one in 1974, or I co-owned the shop that owned it. It was the first NC lathe in my county. We used it to make thousands of parts that wound up in the Tokamak fusion reactor at Princeton.
It's a well-built machine. The hydraulics were reliable, but it was new then. Whether you can convert it at a reasonable cost, I don't know. But I think it would be difficult and would involve replacing a lot of parts.
Ours was controlled by a Bendix 5 NC. My suggestion is that you scrap that before anything else. You'll need to talk to some people who have been through the conversion, or rebuilding, at least. I haven't seen the machine since about 1980.
Among other things, I suspect that it will not have leadscrews, just hydraulic cylinders and some form of feedback to tell the hydraulics which way to push/pull. Converting that to ball screw leadscrews will probably be a serious task -- especially given that you didn't want to risk any modifications to your mill (which, granted, was a lot closer to what you needed already).
I was thinking of that, and about your shop...and that it sounded like you were getting yourself deeper into trouble. d8-)
Converting older machines to modern CNC is quite a nice business for some. I spent a couple of days with a specialist in that trade, in Connecticut, and he was as busy as a one-armed paper hanger. That was around 2002. I've also phone-interviewed a half-dozen others.
Like most of the guys who do that stuff, he was married to just two retrofit CNC makers, who supplied him with a lot of technical expertise and backup.