The grizzly mill is what I consider a hobby grade machine. It will do a fine as long as it taken care of. Now with that said it can not take much abuse. Check with grizzly for the availability of repair parts.
Find recommended cutting conditions from the cutting tool manufacturer. Start with the lowest and be gentle with it.
WWW.use-enco.com and Harbor Freight.com will be good place to start for pricing when you are buying tooling for the machine.
I would not recommended converting it to a CNC. It just is not rigid enough to last very long. Keep looking for a deal or a sponsor for a knee mill with a CNC retrofit.
Just my .02