I recently got my 0759. It took a month and a half to get it off back order. They are selling them faster than they can be put together, probably due to the addition of the DRO. The 0704 is the same base machine, but without the DRO factory installed. The DRO is a feature that you are going to fall in love with if you use the machine much. The 0704 with an aftermarket DRO installed by you will be at least $400 more, even if you get the lowest cost equivalent unit. The 0759 does indeed come completely assembled and ready to go after normal clean up. Mine is smooth, tight, and was surprisingly close to being trammed.
I have not been able to do a lot with mine yet. I have cut some steel with it and it was so much nicer than the smaller Seig X2 that I had before. I had access to big knee mills when I worked. This is certainly not that nice, but it is way better than the little mini-mills. It is surprisingly quiet for a gear driven mill. I can use it in the garage after midnight without waking up the neighborhood.
What you want to do is your most important question now, and get more capability than the minimum you need. You will probably want to do more ambitious things in short order.