Reggie itself calls on it when it needs to. Don't worry about opening the LHDecompressor - you run it through Reggie by opening an LH level file

No, in Newer Messages.bin contains the Message Box messages.

Sure! Just make (/import) a model, all animations, the textures and code its behaviour (the coding shouldn't be too hard).

Good luck!

Yes, that's what I expected...
You can probably import the luma model with animations and textures from the galaxy games. Those games use a different model format though, so you'd have to convert the model to the format NSMBW uses. Then you import the animations, and hopefully they will work correctly. There are a few tutorials on the topic of animations in the tutorial section.

After you have that, the real coding starts. I'd advise you to write it in C++, since it's easier to learn than ASM. You should copy the code of a simple, stationary sprite, and then change little parts to reference your model and animations.

If you have questions on the topic of code, and you can't find the answer online, feel free to ask here. If you have questions regarding models/textures/animations on which there's no answer in the tutorials we have here, you can ask them in the help thread.

sounds uh, interesting. Does that include toad houses as well? what about the cannon and enemy levels? If the map is based around castles I could let you borrow this edited w1 map.
the models like bowser castle are just model swaps, ex: Peach castle model swapped with bowser castle.

oh I thought the cannon would be you boarding a airhip that is flying to another world.

Moved, it was in the wrong section.

Would you mind providing some screenshots?