Q:

What is required to fix this plastered drywall ceiling?

A tree hit our house and made one of the trusses fall somewhat. The structural repairs have been made but I am uncertain how to best repair the drywall ceiling. Originally it was a popcorn ceiling but we had it scraped and skimmed with plaster. Do I use drywall tape and joint compound over the plaster to repair the cracks?
Or could I just plaster over the areas that need repair? 
Or should I chip off the plaster, perform drywall repair with tape and joint compound, then re-plaster?
As you can see, I still need to do some fill in work with the drywall. This picture was just to show the lines where the tape or plaster would need to go.

This picture is an example of how much plaster was used over the drywall. 

A:

This was a nice straight plaster ceiling and I'm assuming you want it to look that way again. I would be sinking those drywall screw to the drywall level, add the drywall to the still damaged area and the plaster over the whole area. If some of the old plaster is loose, break it away first. This should give you a smooth finish to the rest of the wall. I think taping it would be really hard to hide.

