You can also head over to
GameFAQS, and take a look at the Creature List by Dan Simpson. It lists (I'm assuming all) creature codes in the game, but it doesn't tell you exactly what they are (you can generally look at the code and get a good idea).
To run Shadowkeeper, just find and click on
ShadowKeeper.exe. It will be in whatever directory you installed/unzipped ShadowKeeper. It sounds, by the sound of your post, as though you installed ShadowKeeper in your "Override" folder (inside the BG2 install directory). You might try checking there (though you don't have to install ShadowKeeper there).
The first time you run ShadowKeeper, it will search for BG2 on your system. If for some reason, it can't find it on yours, you'll have to tell it where you installed BG2 - either type in the directory, or browse to it.