>>3 Well, yes; but the animation for the most part has to be remade; not sure coding wise; but the scenes, character models, the maps, everything you could potentially interact with; Those are alot of textures, models and animation.
While the music itself yeah, is just a remaster/remix/whatever, just updating; most everything visual-wise they have to add alot to as well as getting it up from the blocky graphics and lower quality music it's at to something on the PS3 like the more recent Final Fantasys.
I should've said "remake most everything from scratch" since alot of it does need to be remade. (hence it being a remake and not a remaster, like they're doing with FFX and the texture/model updates). Not sure coding wise, but I'm sure some of that will need to be remade/updated as well.
Also, it's really cool they're getting the original team back together. Not many companies do that. Plus, who knows, they might add a few side things that were in development back when the original came out, which would be neat since they know what they're doing.