1. Download and install Notepad++.
It has support for markup language such as xml, making it ten times easier to find/hide sections and keywords. AND, it has support for side-by-side view of files(move to other view) + synchronous scrolling, so you can view the original and your edited file at once.

2. Backup the original to a new folder, so you only work on your mod.
When editing data files, you can leave out non-edited values and add comments to keep your mod sleek and discrete like shown below.

3. One important thing is that you need to include the edited indent-sections as shown below.
If you don't, the game will refuse to load the .sbc/.sbs. or might even crash.

4. Here is the editing in progress in notepad plus.
Comments in red have been added in paint. Also, you only need to include & close MAIN indents, plus the indents you actually edit; not all indents in the file.
.
5. That's it, mod away!
Good coding ethics: use comments all the time, double check your links and remember to close indents/paragraphs, or the file won't compile.

cheers