Advice and general guidance on a potential Fadal 4020HT retrofit

Hello everyone!

I am currently investigating a linuxcnc retrofit on a Fadal 4020HT. The machine is a 1996, and I am as of now unsure if it has AC or DC servos. Still figuring out if I am going to go ahead with purchasing it...its potentially a steal!

So background, I am already pretty familiar with linuxcnc. I have a gantry mill that I built from the groundup running linuxcnc/gmoccapy that I make my living with building guitars. Looking to move to something more powerful with an ATC and so I'm shopping VMCs.  Might sound strange but they are a standard for a lot of guitar manufacturers and would greatly improve my workflow.

So this 4020 is from a good sized machine shop, it is under power but hasn't really been used for about a year.  I was able to inspect it and mechanically it is in great shape. There appears to be some sort of problem with the spindle orientation sensing on it. It is running an old 88HS control right now. 

My intention is to potentially purchase this machine and move it over to linuxcnc with probe basic.  Any general guidance or tips from people that have been down a similar road would be greatly appreciated. I also have a few specific questions:

• Since I'm using linuxcnc, is it reasonable or a good idea now or in the future to change the spindle drive over to a modern VFD while retaining the original spindle? I know these spindle drives can be a big cost and difficulty when they go out. I'm also not sure how compatible the existing drive would be with linuxcnc control.
• Related to the above, I am interested in running this conversion on single phase power if that is possible. I believe the servo drivers all ultimately run on DC power, whether they are AC or DC servos, correct? In that case, if I were to also be able to run a VFD from single phase I should be able to avoid the phase converter route. 
• I have not had much luck finding wiring diagrams that give specifics about the lines for the encoders/resolvers on the servos. Does anyone have a good reference for their detailed function to help me figure out how to interface with mesa cards?
• What is the general opinion on homing and limits for fadal conversions? This one, like most or all of them, has that cold start system where you line up the marks on each axis and let the resolvers/encoders do their routine at startup. As far as I understand it has no limit switches or scales or similar. Is it preferable to mimic the same sort of system with linuxcnc or install some sort of homing switches?
• Has anyone had any luck interfacing a jog wheel interface on a VMC with linuxcnc? I would absolutely love to keep that function.

Thank you in advance for any insights you have to offer!

You may be able to rework it to run on single phase. I haven't done it myself but i've heard reports:
www.practicalmachinist.com/forum/threads...han-expected.429807/

We have an old 3016 with the 88HS control in our tool room that we run from time to time. I find the built in control pretty ok and there is a lot of support out there for spare parts still. We use one of these: www.calmotion.com/product-page/lanusb-fad
to drip feed large programs and load smaller programs from USB