This is an easy one with several possible solutions.
The BIS way is to create a gamelogic and give it a bunch of waypoints. In the activation field each waypoint put one line of the conversation, and also give the waypoint a delay in its timeout field. You'll need an initial waypoint synched to a trigger to hold the gamelogic back until its time for the conversation. I pulled together a wee tutorial on gamelogics, its in the Editors Depot under Pending since it only just arrived there.
You can also do it in a script file. If you're not familiar with scripts read snYpir's Friendly Intro to Code Snippets and Johan Gustafsson's Scripting Guide. The critical script command to create a delay is ~. So for example
loon1 sideChat "blah"
~5
loon2 sideChat "moreblah"