Unity Gui from text file templates

Firstly, you'll want to use some sort of serialization. I've found that the XmlSerializer class in the .NET framework is an excellent tool for this, that allows for relatively simple and powerful control over precisely what gets serialized, and how. Plus, XML is reasonably easy to debug, since the data is saved in plain english (assuming you set it up that way).

Unity's GUI system, as it is now, does not function on a basis of "components" or "objects." At least, not on the surface (any of the parts of the engine that users have access to). However, with the 4.6 update that is supposedly coming sometime this Summer, the in-game GUI will be changed pretty dramatically (more info on that here), so don't get too used to the way Unity's in-game GUI works, right now.

Basically, the entire thing functions on a select few callback methods/functions (depending on whether you're using C# or UnityScript/JS) that are executed by the engine, at certain points throughout the game's lifetime. For GUIs that are in-game, the vast majority of these calls will be to the OnGUI method/function, which is actually a shared nomenclature over much of Unity's systems (including EditorWindow, which is an editor class, which means it isn't run in-game).

Within the proper callback function, you can make calls to static methods in the GUI class, and the GUILayout class. There are a number of minor differences between these two classes, but the biggest difference is that the GUILayout class automatically manages the positioning of GUI elements, where with GUI, you have to define the Rects (rectangular area objects) in which the GUI elements are defined.

If you want to save parts of GUI elements, what you would want to do is to create a class that will represent how your GUI element will look and function by holding the data needed to make the method calls that would otherwise "manually" create that object, if they were written directly in the OnGUI method.

So, for example:

public class GUIButton
{
    string text;
    Rect position;
    delegate someMethod;
}

The delegate could be replaced, depending on your implementation, by making the class into an interface, but then the data would be more complex to integrate, and I can't even begin to fathom how one would serialize an anonymous class. Delegates are easily changed at runtime, as well, so you could easily change the functionality even within a single button object, without re-creating it, and removing the old one.

Beyond that, again, you'd need to handle serialization/deserialization, somehow, which is a bit of a task in itself. I'll link a few places you might want to go for more info here:

Unify Wiki Article- Saving and Loading Data: XmlSerializer

GUI Class Tutorial

GUILayout Class Tutorial