Will walls need re-plastering after removal of painted wallpaper?
You won't need to re-plaster regardless. If anything, a light skim coat will flatten things out after paper removal.
My approach would be to peel and scrape away as much of the paper as is practical using common techniques--putty knives, steam, paper adhesive solvent. Once that's done and the wall has dried, seal it with a good primer to lock down all the paper fibers. Now skim with joint compound and texture if desired. Prime again and paint.
I would not add wallboard. That creates problems with drim, door jambs, etc.