I assume you have already checked out the "Dark Dungeon" tutorial.
I you haven't, then that's an fps game, which you could study. I think it is a bit messy though. It's not object oriented, it just uses plain old C structs, strange since it is 1700 lines long and just begs for some classes (being an fps also)!
This is something I don't understand about the C++ version of GDK. They have tried their damndest to avoid using classes in every kind of way, when in reality that is exactly what game programs, especially FPS-games, is asking for!