The main things you will need to know before attempting this is basic HaloScript, and how to set up AI encounters and command lists.
To get a list of HS commands, open up sapien and type script_doc into the console to get a complete list of commands dumped into a file in the Halo CE folder called hs_doc.txt. Look at hs_doc, look at my sample scripts, and do a little trial and error to figure out how stuff works.

Making a Solo Scenario Tag
Mid-Game Cutscene Tutorial
Trigger Volumes for Dummies
Navpoint/Waypoint Tutorial
Solo Map Rules of Thumb
Enjoy.