I would imagine that most hotels in Venice are open 24-hours. I would contact your hotel and let them know that you will be arriving very late, and I’m sure that they will be okay with that. The Hotel Principe is located very close to Piazzale Roma and the train station. At your hour of arrival, I would take a taxi to Piazzale Roma and walk from there; it’s just a few minutes. Waiting for a bus will only delay you further, and the taxi fare from Marco Polo to Piazzale Roma is reasonable. From Piazzale Roma, take the bridge over the Grand Canal, walk past the train station and Hotel Principe is right there on the canal.