$850 parts and labor is not right my friend... even cheap ass parts for a full rebuild is more than $800 not including labor? Maybe if he is only replacing first gear and a servo motor but no way a full rebuild can cost that cheap.
You would be surprised how inexpensive transmission parts are. If you haven't broken any hard parts and the electrical is all good, you can fully rebuild your trans for about $200 in parts. This includes all frictions and steels, soft parts, pistons and gaskets.
Heck, when I broke my input shaft earlier this year, a new input drum, reverse drum, full rebuild kit and a band only set me back less than $400.
A rebuild cost is all in labor. Both to pull it, rebuild and then reinstall.