Your better off getting half a sheet of sheet rock. Maybe a 2x4 as a nailer. While you could scre the hell out of that and re-plaster it will never come out as nice or as easy as replacing it with sheetrock. My whole home is plaster and lathing..I hate the crap! Use a sheetroch knife to remove anything loose and even up the edges. Depending on where the studs land you may need a 2x4 or some kind of wood nailer for the sheet rock. Plaster is cheap and cures very hard. You may find it easier to just use modern mud aka joint compound and tape