I got a small question. We just started with Directadmin and everything is working fine. The only modification i want is to change the Directadmin logo in top of the screen.
Yes, you need to change skin files.
Default skin's files are in /usr/local/directadmin/data/skins/enhanced.
But the enhanced thin is replaced by a new version with every update, so you will have to create your own skin based on enhanced skin.