Can I change app-specific sound files?
Dexplorer opens installed APK file and displays info from APK. This is internal application resources, build when autor compiles APK.

To replace specific resources you must decompile APK file, repleace files and compile (build) again.

On new build you must sign APK file with your own certificate (you may generate it). Only author have original keystore to build signed APK file.

App author probably won't provide his application signing key.