Ok, you guys are probably really annoyed with me asking this question so many times, but why is my game not reading my mission.lvl file. Could someone write me a list of what possible reasons my game isn't reading it? Thanks.

Check your mungelog, if the game isn't reading mission.lvl correctly (I assume this is a map and not a mod) it will give you an error.

Mungelog? I'm hexing a shipped map? Sorry if this is reallt n00by.

Yeah, can't really help you there. If you overwrote the wrong byte, added a byte or removed a byte it's not gonna work. My advice is to make one small change, test. Make one small change, test. Rinse and repeat. It sounds like it takes longer, but if something goes wrong you know where it is, so you're not spending countless hours debugging.

I tried change hero on Coruscant - no luck. Nothing at all happened.

I wouldn't recommend hex editing if you're going to release this as a mod. It's gonna break multiplayer (I know from experience) which people don't like.