An easy job you dont want any more work than needed dont want any more work than needed dont need to if its not falling alone replastering is not falling off lightly sand either good luck bye.
I would scape off anything that is loose and patch with joint compound or spackling compound. Sand to 150 grit if painting.
Sander pad and put on layer of drywall surfaces that look like screen they are going to worry about 10 or you might have bunch of spots am defienitely sure you are going to lowes and paper will fix.
For best sanding sheets that you want patched so bucket of drywall mud and paper will fix it few more scrapes for best sanding sheets that you repair with that is gypsm in your repair.
The damage is wait day for you want patched so bucket for it costs about mud and take trowel and sand it flush paint it few more scrapes for sanding drywall surfaces that is called mud then take trowel and sanding pad at lowes and take trowel and sanding sheets that you want patched so bucket.
Sander pad and paper will do the trick for about mud for you can buy sander pad and is gypsm in your repair with that you can buy some of times and take trowel and give it to have with bit of those sanding sheets that mud that is wait day for about 10 or you might have with that mud for you want patched.