What did you decompile? o.O
As for flipping textures. If your using GTKRadiant 1.5, select your brush, turn on texture lock (on the toolbar with a padlock i think), and rotate it using the xyz buttons to what you want. I usually get mixed up with them, so i just rotate until it fits what i want. Don't forget to turn texture lock off afterwards, or you might get mixaligned textures somewhere else.