nsIHTMLEditor vs. nsIDOMNSHTMLDocument, General Editor questions

I need to integrate an editor into my Java application. The most
apparent way is go with javaxpcom. The basic hookup is pretty straight
forward. However I do encounter quite some problems when I get to the
details of customizing the editor and/or providing extended behaviors.
For sure it has a lot to do with my lack of knowledge with Mozilla
internals. So here comes a few of my questions:

1. Are there any good resources (documentation, tutorial etc.) you
recommend on programming against Mozilla editor?

2. If I embed a nsIWebBrowser and then make it design mode using
nsIDOMNSHTMLDocument interface, is this the same as using
nsIHTMLEditor(or nsIEditor) interface directly?

3. I have seen editorOverrides.css, forms.js etc. mentioned in few
posts to customized the look and feel of elements in editor. My
question is can most of the customization be done this way without
resort to C++ programming?

4. The look and feel when an element is selected is quite different
for different elements. For example, the img when selected shows a
resizable border while the form input when selected is highlighted in
blue (similar to text being selected). How can I make them behave the
same? Where should I look (or is this something one has to modify the C
++ code)?

Any comments appreciated. Thanks.