First CNC project

I am working on my first CNC Router project and have some very basic
questions I know this group can help with.

My first tool will be a small 3 axis CNC Router. I purchased, off
ebay, a small x-y-z bed with the stepper motors attached. I haven't
seen it yet, but understand that I need stepper drivers. I purchased
Gecko drives to handle the size 34, 300 oz motors, and should have no
problem wiring them.

Question #1. How do I interface between a PC and the stepper drives?
Question #2. Do I connect throught the parallel port? What
limitations exist?
Question #3. Why do some larger CNC Routers (other tools) use a PLC
between the PC and the drives?
Question #4. What software should I use to interface the PC to the
CNC?

Thanks for the help.
Tom