You don't need to book the ferry well in advance, but for a rig of your size it might be good to book a few days ahead. Which ferry are you taking, to Argentia(14hr) or to Port Aux Basques(8hr). Many arrive by one and leave by the other. There is no need but some people do.
There is loads to see and do here. Just about evry small town has its own festival. A huge variation in scenery from the grand mountainous beauty of Gros Morne Park to the traditional seascapes of Fogo and Tilting. We have 1000yr old history at L'Anse Aux Meadows near St. Anthony to more modern history at The Rooms in St. John's detailing the 100yr anniversary of Beaumont Hamel and The Royal Newfoundland Regiment during that battle in WWI. And of course we have icebergs and whales all along the northeast coast.
I included a link to Tourism NL to help plan your trip.
Tourism NL
