I'm a total noob here, so bear with me. I have an idea for a simple horse merchant mod, and, for starters, I'd just like to modify the merchant's dialog text. For example, you can interact with Cedran outside of Markarth and ask him, "Can I buy a horse?". Where the heck is that string stored? I feel like I've looked everywhere.

Or, even better, if someone could direct me to a tutorial that shows how to create custom NPC dialogs, that would be absolutely fantastic!

creationkit.com , Go to tutorials and look at the quest tutorial, it shows you how to edit dialogue

Thanks a ton, that tutorial gave me the last clue I needed to find this data. I didn't know that info was stored in a quest object. I used the "Use Info" tool on the Cedran NPC to find the "stables" quest that contains the dialog i was interested in. Cripes... talk about looking under the last rock.