Help System

I've been thinking about how to implement a help system for TPAS. My first thought was to add 'context sensitve' help links (ex [?] ) in places were I think help might be useful. When the user clicks on the link, a popup window or CSS popup is displayed witht the help. All of the help entries would be stored in the database system and would be accessed though a PHP class. An index of all the help entries could be easily generated. Instead of storing the help in the database, it could be stored in files (plain text, psedo-html, or xml) and read by the php class. What do you think? Is this overkill? not enough? just right?