How to Hack Games? (Interested in The Viceroy)

[Rakeela]

There's a game that VERY much held my interest called The Viceroy, but I have serious qualms with its behavior.  I've noticed a lot of anomalies while playing it.  It doesn't have any kind of modding or open codebase associated with it, but I did discover how to do some minor savegame edits... VERY minor.  Yet more important to me than that, is that I'd like to do some full-fledged fan-patching.  I want to know why the game misbehaves and I want to produce something that behaves differently in important ways.

Is it possible to seriously break into a game and start modifying it in ways that it wasn't designed to be modified?