Basically, you should avoid changing the 'Topic Text' section if you're adding dialogue to an vanilla topic. If you're changing what the courier says in a vanilla dialogue topic, you should enter your custom dialogue option in the 'prompt' section under 'info details'. To revert the 'Topic Text' sections you've changed back to vanilla, you'll have to open up FNVedit and overwrite the 'full name' entries that you've changed. That just involves dragging and dropping the vanilla 'full name' entries onto the ones that you've changed. After that, I'd use FNVedit to clean your esp of dirty edits. Sorry, this is quite a quick response. I'll check back later to see if you need any more help.