First, careful when bumping dead threads, you will just get people to not like you that way.
Second, there are tutorials around this and kcmm forums, as well as in youtube.
You want to mod the iso to play in dolphin, right? Use Wii Scrubber and replace the files you need with the mod's ones. That's really all you have to do.
Want to mod characters? Download Brawlbox and open the character's files to see what's inside them.
Expanding your roster... search around for BrawlEx. This one is hard for someone who knows nothing about brawl modding, so I suggest you to not do it yet.
Keep in mind that modding characters mostly consist of working with 3D models and coding, which are two very large topics, and finding people to help is rare, so get ready to do everything on your own.
From my experience around those communities, very hardly anyone will tell you step by step of what you have to do to mod a character. You must go after it yourself. Download the tools and try learning on your own, even more because 95% of the people don't know how to mod, they just know how to use mods.
After you get used a little to brawl modding, if you want to understand how coding works, I wrote a guide some time ago explaining the main commands:
http://forums.kc-mm.com/Gallery/BrawlView.php?Number=213305
If you know absolutely nothing about programming, that can be tough. I didn't write any explaining 3d models, though.
