Complex sentence: Elaine Stewart was the card dealer for the CBS version, while Beverly Malden filled this role for the first half of "Las Vegas"; for the second half of that run, she was replaced by Lee Menning.
Split into simpler sentences: Elaine Stewart was the card dealer for the CBS version. On the "Las Vegas Gambit" version, the card dealer was Beverly Malden; she left half-way through the series' run and was replaced by Lee Menning.