The two closest programs that could do what you hope to do are Utility of Time and any generic hex editor. If you can somehow find a way to convert the model data from Kingdom Hearts into an F3DEX2 display list fully compatible with Link's hierarchy and animation structure, then it should be a simple d-list swap. But I seriously doubt the N64 engine is capable of rendering Sora's model, let alone in addition to other actors and the rest of the map.
In layman's terms, this is impossible, and doesn't belong in the codes section (even if it were possible, only a hack--in a very loose use of the word--could accomplish this).
I'm not sure if there's a way to rip textures from PS2 games or not, but I believe there is. But as I said multiple times before, this is an impossible thing; even if you manage to rip Sora's model, hierarchy and animations and convert them into a display list compatible with Ocarina of Time, the N64 engine cannot handle models as complex as the ones on the PS2.
You can try using a PCSX2 graphics plugin to dump textures, but I don't know if they have a plugin that does that yet. Don't ask me how to set up that emulator, because I've never done it and don't know the process.
Let me put it this way, PS2 character models CANNOT be ported into an N64 due to incompatibility of model format AND the N64 can only handle so many polygons being drawn on the screen along with a certain amount of textures. The N64 is not made/built to handle complex models like that.
Seriously give up now why you are ahead it is "SERIOUSLY" impossible.