Terrain transforming?

Hi i’m wondering what would be the best method to update the vertices of a model (the terrain) given a point in 3d space by raycasting. I would like to add some noise to the vertices to allow for realistic looking sculpting. I also would like to know how you update the specified vertices without updating the texture coordinates and the normals, also only updating the effected vertices and not recreating the entire mesh. If my question doesn’t exactly make sense please ask! Thank you also I can provide snippets of how terrain is generated and how i’m raycasting if need be. Thank you!