Debian "etch" does not seem to include glade-3 debs. This is very strange to me. I found this post: http://lists.ximian.com/pipermail/glade-devel/2006-June/001245.html
which links to to a .deb that might work.
In looking at the packages for Debian 4.0 (etch) I see that it has software that is mostly too old to install Glade 3 from source without upgrading a bunch of packages including GTK+ (debian 4.0 has 2.8, glade 3 requires 2.10, latest is 2.12). I don't know Debian--I'm using Ubuntu--but that seems strange to me.
The "testing" release of debian, code name "Lenny" has all the dependencies and glade-3 available. Don't know if that's a option for you.
If you were to try to install from source, you're going to have to first install 'pkg-config' from apt-get and then you will have to install all the dependencies as well (which the ./configure step will tell you). That's a lot of work.