plaster repair/replacement

We would love to fix up the somewhat damaged plaster walls in our prewar co-op. We’d like to maintain the look of the large moldings, but they and the walls are puffy, caked with peeling paint, and have had shoddy repairs in quite a few places. We’ve heard a few recommendations, none satisfactory: tearing the moldings down and putting up fresh sheetrock over the existing walls; performing spot-repairs in the worst areas; etc.

Does anyone have experience in this area? Is chemical stripping an option for the moldings, door frames, and window sills? Would spot-repairs on the walls just be putting off the problem? How much might all this cost? Any help is appreciated.