tonofsteel:
It takes a lot of time, patients, skill, and money, to build a milling machine that is accurate enough to be anything more than a boat anchor. Before you go spending a ton of time (and money) building your own machine there is another option you should consider.
Since it sounds like you want your project to be based on the electronics/CNC end of this machine, you should look into converting a mini or micro mill. Harborfreight sells the
mini for $500, and the
micro for less than $300.
That would leave you to do just the CNC conversion, and in the end you know that you'll have a useable (small) milling machine. Several people on here have converted these, so there is plenty of info on what you'll need for motors and other hardware.