Motor Size

Hi All!

A few quick questions:

1) How do I determine what size stepper motor to use? The CNC is a
gantry type with a 2' x 2' cut with a 5-6" Z. The construction is
mostly aluminum. For the ways I am using 1" dia. Thomson shafting
with linear ball bearings. The drive train is .625 ball screws. I
plan on running 2 screws on the X axis. The main purpose of this
router is for 3D milling/routing in wood and light engraving in
brass. It would be nice if the rapid is in excess of 200 ipm. If that
isn't feasible....

2) I need a gecko for each motor, right? Can I use one drive to
power two motors on the X axis? If so, is there anything different I
should know?

3) I should have a limit switch at both ends of the axis, right?
I guess that's it for now....
Thanks for the help
Seth