Introduction & request for help

Greetings~!

My name is Weyland Smith.
I subscribed at the recommendation of one of your other members.
I am very interested in learning more about building CNC's,
but am finding it difficult to sort out the information I've found so far.
Hopefully you can help me decipher some of it.

I want to build a CNC plasma cutter
and if it goes well, I'll convert my mill.
The construction part of it is of little concern to me as I'm
a tool & die maker, and have my own machines I can use to do this.
I also build computers on the side, and so have
access to many parts for that aspect as well.

My problem is this -
I want to use a PC to control the stepper motors
I've planned to use for the project, but am very unclear
on what exactly I need.

I've surfed and surfed, read many a page, and just can't seem to get
my simple mind around this part.
As with many I've read about in my searches, economy is an issue.
I don't have much money, but do have time and a willingness to learn.

Once the structure of the machine is built, and the
motors attached, what exactly do I need to make it run from a PC?
Once I write the code, how do I get it to run on the machine?

I've seen and collected many of the programs out there,
but really don't know *which* I'm supposed to use, due to my ignorance.

Any help you can give or direct me to is greatly appreciated.

Thanks,

Weyland