Lathe Ballscrew Questions

I have a Nook (Chinese)14-40 Lathe and am starting retrofit.
I have about finished my Lagun Mill.
1. Do you replace the acme thread shaft or the feed shaft or just
add the ballscrew in a new place for the Z axis?
2. Do you replace the cross slide acme screw or ? for the X axis?

Any one who has pictures or plans I would be grateful.

Thanks .... Jack Hoffa