How much to sand down walls/moldings?

We just stripped original decorative moldings, window frames and beams. It's not cheap (ours cost a few grand but we had a ton of work to do). In our case the job was done with a chemical, not by sanding. Unless your moldings are special in some way, I may be more inclined to take them out and replace rather than spend the time and money to strip.

Walls, if they are heavily coated with old paint, will likely need scraping and replastering. If they're not in good shape, you might also have to skim coat, which is more expensive. Cost will really depend on your walls' condition.

Just replace the moldings. Most modern millwork is made using the same patterns as the old, vintage moldings, so it is usually pretty easy to match an existing molding.

The paint shouldn't be peeling off the walls, though. That's a bit odd. Moisture under there? Or did you mean paint peeling off the moldings only?

If paint is actually peeling, then it is quite possible latex was painted over oil paint. That results in the latex eventually peeling away and always being very fragile in terms of scratches since it cannot adhere properly. Ask building super if any handymen/contractors regularly do work in building and consider contacting them to discuss.

It seems that it was more chipping than peeling, although I'm not expect so I can't say for sure. Thanks for the advise on replacing the moldings, that's not a bad idea. And I'll try getting in touch with the building super and seeing what we can do about finding someone to check it out.