Ceiling sheetrock

I need to remove all the ceiling sheetrock (moisture damaged, roof leak, mold, cave in) and put up new sheet rock and new insulation. All 3000 SF of it.

Is ceiling sheetrock typically estimated as a $/SF, or is it a case by case depending on how many high hat lights cut outs, how many odd shaped soffit boxes etc...?

Is it better to hire out the whole project or is it better to break it into stages and use different people for each?

- Demolition (remove old sheet rock, old insulation, remove fasteners, dumpster rental, haul away, disposal).
- New sheet rock install, patch and sand.
- New insulation in attic.
- Paint new ceiling.