questions about modding traits and buildings

Hey. I wanted to try a game with less micro for my family members, so i edited the triggers in the export_desc_character_traits and set the chances for all bad traits to show up to 0 (i used ctrl+f to find all the triggers for a particular trait). However, when i started a game, at the first coming of age the new member still ended up getting one or two bad traits. I exited and double checked all the triggers for these particular traits and they're all set to 0 chance. Am I missing something ?

Also, if I wanted to give a faction the ability to build a building they can't normally build, do I just have to change the 'requires faction' bit in the export_descr_buildings, or is there something else I'd have to change as well (like assigning a picture for this building since some factions have different versions for the same type of building) ? Specifically I wanna give the Barbarian faction tech level 4 stuff so they actually put up a fight ^_^. Thanks.

Oh yeah, and changes to the export_desc files affect the AI too right ?