[Highland Park] solutions for a sandstone foundation w/crumbling exterior??

Most of our homes have sandstone foundations....ours is crumbling on the exterior of the house. Has anyone had this repaired? Is it a cleaning & painting repair, or a job for a masonry contractor?   I don't know who to ask for estimates, or how to assess who seems to know what they are doing because I don't know what sort of work it is.   I'll post a summary of responses to the list.   Many thanks in advance for any suggestions! Mary