problems changing a GtkImage

["happy programmer" <motif4ever gmail com>]

I am attemping to make a basic image viewer in Linux, (app checks a
hard coded directory, puts *.jpg file names in a GtkMenu object,
displays the names in a GtkOptionMenu widget. Selecting a file name
will display the image in a GtkImage widget.

When I hardcode the specific file names, I can get the GtkOptionMenu
to list the files. The default (top/first) file automatically displays
in the GtkImage widget as expected. But, selecting a different image
does not change the GtkImage, it remains static, stuck on the first
image.

What am I doing wrong? I tried using g_object_set_data to change the
"file" parameter of the GtkImage object as part of my "changed" signal
handler from the GtkOptionMenu, but this doesn't do anything, or
causes weird crashes, or gives compile time errors. This is a very
simple fancy hello world for me and I'm totally stuck.\

Thank you in advance for any help or suggestions with this simple but
frustrating example.

P.S. Is there a good GTK/Glib/Gobject tutorial other than those at
gtk.org and in "The Official GNOME 2.0 Developer's Guide"? I could
really use something as well written as "Mastering Perl/Tk".