How do you change the dialogues with AI Civs?

[Copper Beeches]

I really don't like some of the 'funny' things the AI civs say on the diplomacy screens. Would it be easy for me to change them? I don't want to change the effect on play, only the way the AI says things.

 

[Refar]

The text in inside Assets\XML\Text. Distributed over a few files, unfortunately, should be still easy to find searching for specific quotes.
The Dialog is assigned to Leaders via Assets\XML\GameInfo\Civ4DiplomacyInfo.XML (You don't necessarily need to change something here, if you only want to overwrite a few Quotes, just change the text files).