Hello. I would like to ask if it is possible to replace sounds in the vanilla game? Not a mod map,the stock maps. I plan to change the sounds with EABF's sounds (mod will not be released). Thank you.

Yeah, in theory it's possible... have you worked with sound in SWBF2 before?

Someone feel free to correct me since I have been out of modding for half a year at this point... but:
The biggest difficulty is that, after everything is munged, all sounds are lumped together into just a few different .lvl files. And I mean all sounds, with the exception of map-specific sounds. So if you want to just edit the sound of a Rebel soldier voice-over, you will need to correctly compile all of the Galactic Civil War era sounds and munge them properly into the gcw.lvl sound file. So it's a lot of work and I know Marth8880 and one of the mods managed to extract and separate most of the raw sound files but I'm not sure if they got them all so you might have some missing.

Again, this may all be incorrect as I haven't worked in the mod tools for a while now and I'm just resuming modding again.

In a mod, you would call your own sound.lvl on top of the stock sound.lvl but your sounds would have to have different names to the stock ones otherwise the stock ones still play.