The island of Venice is very walkable from the Santa Lucia train station to St. Mark's Square and all the areas in between. If you buy a one-day pass for the vaporetto (good for a 24-hr period), you can visit Murano on your own and take the #1 (local) that goes up and down the Grand Canal. Don't forget to validate your pass at the yellow machines by each vaporetto stop every time you get on and off. We visited Murano on our own. It's a lovely island, but it does take time to get there and back. I'd rather see the inside of the Basilica first than visit Murano if you have very limited time in Venice.