Do sea snails shed the conch and move into a new conch?

No, a conch is a mollusk which lives in a conch shell ,which it secretes itself. As the conch grows the shell gets bigger too, to accommodate it. Sea snails tend not to have any shell at all and if they do have a shell it is one that they secrete themselves. Hermit crabs live in the empty shells of mollusks and move to a new shell as they grow bigger.