Take a shuffle over to MAJOSOFT's site (you can google that). He's done quite a bit in that DIY size and has some online software that will generate Gcode from text (save a bit of $$ there too.) A trial version of MACH2 should get you started . A system that size could mount right on top of the pc case and keep the footprint real small - not as small as a system you originally thought - but easier integration. Moving small bits- means smaller stepper motors and less expensive controllers. You could try and do it all with floppy drive motors - a fellow in New Hampshire has some good info on his site - I'll look and repost as I have time...
Good Luck, Jim
Experience is the BEST Teacher. Is that why it usually arrives in a shower of sparks, flash of light, loud bang, a cloud of smoke, AND -- a BILL to pay? You usually get it -- just after you need it.