Not a small job but with the parts can be done in a day with luck and hustle.  If you have a good tech that isn't busy, has done them before, and the parts are there you could help him to get it done faster.  When we did our 9770 it was a second combine and no beans were ready so we worked on it in the mornings for a couple hours while the fog burned off and on a rain delay finished it up.  S670 we helped the techs but it was a shop mistake on the PIP that made it necessary to do again.  They didn't put the front crosspiece on the chaffer frame and the chaffer was really bouncing good when we started corn.