Audio Replace sounds inside an asset.

Hello everyone
I am actually totally new to unity but i did some searches and couldn't find a solution.
Here's my problem : i'm a young sound designer and engineer and i've been in touch with some developpers to work on a game that is curently in early acces and we talked about demo clips.
So i wanted to know if it was possible to edit an asset to replace the sounds inside it. And if yes what would be the tools to do it.
Thought it was preferable and more relevant to do a mod of their game instead of edited videos clips.
Hope someone can point me on where to dig. thanks