I haven't built one or seen the plans, but I'd guess $2000-$2500. Yes you can reuse the G540 and the motors, but I think you'll need an additional motor. I would not consider using 1/2-10 acme, unless it's at least 2 start or 5 start. Sounds like you have single start, though, which is not a good choice at all, unless you want a really slow machine. If you go R & P, you'll need 3 of these, plus the racks. That and the 8020 are probably the biggest cost items.