The ride is relatively easy with a few gradual but easy climbs. The look from the top over Lake Superior is fantastic. Take the earliest shuttle over and make a day of it. I enjoy the clockwise ride. Last shuttle off is 4:30 you can camp on the island if you want but permits are needed. The ferry ride in 2008 was I believe under $10
only way to Grand Island is through the ferry or other boat. The shuttle service is just outside Munising and well marked.
http://www.singletracks.com/item.php?c=1&i=3544