Modifying existing animations?

Recently, I decided to try modding for Heroes 5. I found out how to extract animations, models, and skeletons. I can import the skeleton into 3DS MAX and animate it, but only after a long and tedious process of adding Inverse Kinematics and other things that I haven't fully figured out yet. Is it possible to modify existing animations? They are in the .ma format, but they won't import into Maya 2009 or Maya 6.0. An error occurs, stating that the file cannot be read - Syntax error. For example, I want to change the idle00 animation for the Hellhound – I need to make it so that it doesn't stomp its front hoof. I extracted the animation, but again, it won't import anywhere. I don't really want to re-animate everything through the skeleton animation (which I haven't fully figured out yet), especially since it requires a lot of preparatory work. I may have searched poorly, but I haven't found any good guides on animation. Maybe someone can help me with this?