Maccnc,
What kind of problems are you having with the backlash with mach3. I have usually gotten excellent support from Art of Mach3. Tell me what not working right. And go ahead and go to the mach3 website and check with art and I sure we can get you a good answer. His link is
http://www.artofcnc.com and just find the contact us link and let him know what is going on. He has always got back to me in a day or two.
Did you catch the technique that JL123 used to preload the bearings, using the pipe clamp. This might be helpful after you replace the bearings in the ball nut.
I think you will have a excellent machine once you get the bugs out. If you need help, shout out and there are plenty of folks to give suggestions.
Hope this helps,
Ron