Yep i though about this. I know that the server has some files too.
But i have the client of the game, and before trying to change the code , i changed some clip's pictures into my client file and it works.

I got the code with Flare ( it decompile all the actionscript of the file, but only the actionscript and this script is not editable, because flare can't recompile it ) , i also use SWF decompiler, i can take a look at all the scripts, clips, shapes...that are into the main swf file. but, in that case too, it is not editable.
Actually, it should be editable, but when i clic on "convert to .fla" i got many "stack underflow" in the conversion's column and the software quit.

So it seems that the only solution a got is to shunt the script by insering a peace of code into an other clip.

I know that it is possible to do that but i'm not good enough with script to do that