The Marvel part is actually only a small section. It would be a major effort but we're talking 10-15% probably. The Hulk coaster could just be repainted, it doesn't really have any Hulk functionality. The Spiderman ride would be a bigger effort but since all of the spiderman specific stuff is video that isn't impossible either. The Marvel section makes heavier use of people in costumes walking around than it does the licensed rides in Marvel terms.
EDIT: there's also the Popeye ride, now that I think about it, but not sure if that is Marvel or a comic strip syndicate. Either way IoA is huuuuuuge and only a section of it is Marvel. The rest is (custom) Lost Continent, Dr Seuss, Toon Lagoon (comic strips), and Jurassic Park. There might be one section I'm not remembering...