[mythtv-users] Need advice on customizing my UI

[Azmat]

I've been successfully using MythTV for about 8 months now and I
decided that it was time to delve into its inner-workings so my
Myth-box can be all that it can be.  I built my first system from RPMs
and it works great.  To leave that system undisturbed, I decided to
install 0.19 on a second "sandbox" system so I can play as much as I
want.  I wanted to start out small by customizing the layout of my
frontend: rearranging menu hierarchy, modifying buttons, and possibly
adding buttons that link in to other programs.

I hit a snare early on that has me a bit confused.  I understand that
the files that describe the UI are XML and are found in
/usr/local/share/mythtv, however I'm confused as to the mapping of
these files to what I'm currently seeing in Myth.  For instance, in
0.19 on the main menu, my choices are:
Watch Recordings
Upcoming Recordings
Schedule Recordings
Recording Priorities
System Status
Utilities/Setup

However, according to mainmenu.xml, it seems the fields are:
Watch TV
Media Library
Manage Recordings
Information Center
Optical Disks
Utilities

Why is there a mismatch?  I feel like I'm missing something here.  I
also understand that the UI is also dictated by the theme XML files
located in /usr/local/share/mythtv/themes/<theme>.  I notice a ui.xml
and a theme.xml file, however its not clear to me how to use these
files to affect menu layout.

My main questions are:
1. Why is there an apparent disconnect between the fields given in the
XML files and those shown in the actual menus?
2. What areas are each set of XML files responsible for?  Do the files
in share/mythtv control layout and those in
share/mythtv/themes/<theme> control icons, colors, positioning, etc.?
3. Is there a walk-through or tutorial that explains the above two
questions that I'm unaware of and possibly describes some of the
syntax used in these files (i.e. MENU, EXEC, JUMP commands, etc.)

Thanks a ton for the help.
Azmat