ok. i think i missed something. I only need one code, correct? And that code is in this thread:
http://forums.kc-mm.com/index.php?topic=5.0(if i'm not mistaken).
So what i did was copy the code (with the little text above it) and saved it in notepad as a TXT file. The problem originally was that Codemanager didn't detect it. So i deleted all the text above the code. Still same problem. Then i just deleted all the text after the semi-colon, then it worked. I ticked the box, converted and saved as a GCT file (or whaterver format it was).
I put it in the 'codes' folder at the root of the SD card and for some strange reason, when i loaded brawl through gecko 19, it didn't detect any codes.
I'll try again, but there's only one more thing tugging at me. I downloaded the rosalina pack, and kept everything in the folder named peach that it came with. Do i just leave this folder inside the 'fighters/peach' folder (so a fighters/peach/peach folder)?
I'll update as i go along. And i just want to say, though it's my first time, it's pretty awesome going through this hacking experience
[edit] ok. for SOME reason, in code manager, the file replacement code isn't detected. There's boxes to tick for all the other codes, but not one listed for the file replacement code. And when i convert whatevever i have there, gecko STILL doesn't detect any SD codes. RAGE!