I built mine off of some plans I found on cnczone.com
that a member posted. You can find the plans in the forum under one of the sections that they post free plans. I think I had about $300 in materials (mdf, black pipe, all thread, bolts and screws, roller blade bearings, a block of delrin, and aluminum), motors, and the controller. If you do build one from the JGRO design, I'd recommend at least a 200 oz/in motor or larger and acme screws. There are several parallel port based controllers to choose from on the market. Some are kits that you need to solder, but most will do it for you for a small fee.
Learning Gcode wasn't extremely hard and really isn't all that necessary, but is helpful when troubleshooting. Most of the software will convert a dxf (autocad) type file into gcode for you. I also found a freeware program for generating text from any windows font for doing signs and some other software for converting pictures into drawings.
My current machine is slow 11 ipm (inchs per minute) which is why I want to build a larger better quality machine, but it is accurate. It will do just about anything a larger machine does with the same near accuracy, just may take all day.
My latest use for it is laying out degree marks on a new miter guage for my table saw (took about an hour to etch 45 degrees of marks). Found a autocad drawing of a protractor and resized it for the project. With a carbide bit it will etch aluminum plate easily and mark drill marks and make pilot holes where needed accurately.