1. yes you can use notepad though I recommend using notepad++ (google it, its free) which offers a lot of tools that makes modding easier
also you will need to convert the BIN to TXT, there are several of these tools around the mod section of the forums (recommend harpo's tools)
2. I know there is a user made tutorial in the mods section of the forums, also the downloads section has some as well
3. not sure, I do know that there was a mod that had colonizable stars, so most likely, that would be in the Galaxy Forge's area (found in downloads section as well)
4. yes