I haven't written any code in ten years so I'm looking
for something to create GUI Frontends without too much
programming experience.
Zenity is designed exactly for this purpose and comes as a part of Gnome. It is rather old but its limited functionality is almost certainly exactly what you're looking for. The other solutions proposed would be using a cannonball to kill a fly. You could use Monodevelop or Glade if you want to learn C#, Python/Ruby or C, but why bother if you don't have to?