Both. The switching of the discovery of the soft-landed casket onscreen, to much earlier in the film, was supposed to come after Sarek had berated Kirk for not bringing Spock's body home. Some of the dialogue (by Chekov?) was chopped up to create new sentences, IIRC. Vonda McIntyre added details to her novelization, such as how the Hall of Ancient Thought worked, the contents of Spock's will, where Amanda was at such an important Vulcan ceremony, etc.