Oh, that thing. Yea, I ported the Star Destroyer. But the model is very bad... Part of it's texture is gone, and etc... Really. The Star Wars mod here on HLP is much MUCH better.
Imperial Alliance uses a modified exe. So the hud, menus and etc. are unique and everything. And the exe got the file archives in different format too. They are EH. Now, to open them, it's really simply. You need to have the VP viewer. Rename the large Imperial Alliance file extensions ( [large-file-name].eh ) - from EH to VP. Then open them in the VP viewer that comes with Volition's FreeSpace tools and voila- you got it open. Then, it's just a simple bit of modding that you can learn the basics from the "How To Start Modding" thread.