Success ! Thanks to all that contributed.

Hi

Ian Stewart's contribution was the last missing link that enabled me to get my D-Link DWA-131 wireless USB dongle working.
To quickly recall, my problem was that during installation neither the drivers for the dongle, nor <gksu> was installed to enable direct installation from the repo's.
Let me here retrace the steps that led to success, so that others may build upon them in their endeavor to promote the use of Linux:

1. identify the chipset used:
    google for <D-Link DWA-131 Debian>
    The reference to <Debian> is critical, as otherwise you will be directed to web pages selling the dongle.
2. find the Debian package containing the driver:
    Open the proper result page <http://wiki.debian.org/rtl819x> and follow the link provided there to <firmware-realtek>
    This leads to the most recent driver Debian knows about, more recent than the one Ian suggested.
    Follow the links and download the .deb package.
3. Use your Archive Manager to open the package (a Debian Package is just an archive to which come control information has been added in file form) and extract its contents to a separate folder.
4. Inspect folder contents:
    You will find at least two folders in the package. Ignore DEBIAN, it contains control information. Copy all other folders to the target folders on your target system. - Bingo, as there are no dependencies to worry about!


In the case of the missing package <gksu> the steps were as follows:
1. google for <gksu Debian>
    Open the proper result page <http://packages.debian.org/search?keywords=gksu> and follow the links to your target system. In my case, it was <wheezy> and <amd64>.
2. Check that the dependencies, i.e. packages that also must be installed, are already installed on your system.
3. Download the package, and all dependent packages, unpack them with your Archive Manager and copy the files to their target folders, as outlined above.

Done!