The context of this statement might make it appear that the "great things" might have had to do with ship building, but it is much more likely that this is one of Nephi's asides. He went to the mount oft to converse with the Lord. Certainly some of the trips were prompted by questions generated from the building of the ship, but it is almost certain that when Nephi speaks of being shown "great things" that he means things of the spirit. Nephi does not appear to be overly impressed with technology. He considers the Liahona a small thing, and while he required the Lord's help to design and build a ship, he doubtless saw that also as simply following the will of the Lord. For Nephi, the "great things" are always things of the Spirit.