Is this DLC working? I bought it, it downloaded, installed, restarted the game, but Ghost still has old skin in Mission Mode and I do not see any option to change it? Is it broken?

I must agree with Kranch. The skin is not working. Even when I finish the game, there is still only the standard skin in the Mission Mode.
I checked what files are installed with the plugin installer. It installs only some GOG files and uninstall info files. No new game data files or configuration change. It's same with GOG Galaxy or offline installers.
I would be nice if someone from GOG take a look at this.