I created nearly the identical setup last year. I used a Waste King L-8000 Legend Series 1.0hp disposal purchased new mounted in a stainless steel sink.
We built ours a bit bigger so that there's a platform as well as the sink. It came in handy as we had 2 people quartering apples on opposite sides on cutting boards then tossing the apples into the sink with one person manning the grinder.
The disposal did in fact overheat on me after about 45 gallons of cider pressed (about a 10 hour day alternating between grinding and pressing). I'm planning on running more cider/water through it this year as we grind the apples to both help it operate smoothly and to cool it. The apples mush up in the disposal, but a couple of splashes of water or cider will clear it out quickly. I say water/cider as when you're grinding prior to your first press, you probably wont have any cider on hand to run through, so just use water instead.
I'd recommend finding a way to secure the disposal and keep it from rotating. When they are mounted under the sink the piping keeps them from rotating. Since you'll just have the piping emptying into a bucket, the grinder will slowly spin its way around (not a huge problem, but avoidable with some preparation). We just tied our power cord around one of the legs on the stand, but will probably try to figure out a better way of doing it this year.
Another piece of advice would be to put a support underneath the grinder. We quartered our apples and even still had to use a piece of wood to jam them into the grinder. All of the jamming looked to be taking its toll on the grinder where it locks into the sink. The things really aren't designed to be abused like we did, and I think a 2x4 underneath supporting it would help.
The grinder spits out basically applesauce. We found it very easy to press. We were using a tub press that was my great great uncles and the pommace was coming out in dry sheets. I'm not sure the amount of bushels we pressed as we had the apples in burlap bags. I'll try to do a better job measuring yield this year (although I'm working on a hydraulic press setup).
The resulting fresh cider was quite good. I didn't notice any off flavors from the seeds. You'll notice a lot of bits either floating to the top or bottom. I racked off the middle after a day or so.
The grinder with stainless steal sink setup seemed pretty easy to sanitize. I basically filled up the sink with sanitizing solution and then let it drain through the disposal as i ran it on and off. If you can plug the tube coming off of the disposal when the sink is full, the sanitizer soaks the whole grinder.
Let me know if you have any other questions and I'll try to be as helpful as I can!