We need id's, lots of id's.
(not exactly Neo, Matrix)
This slightly expresses the basic concept you should have in the back your your mind when creating Ajax driven, highly dynamic interfaces. Without id’s you are not able to talk to elements if you want to update them, eiter value, innerHTML or events.
Make sure you have a fallback for non-javascript users. When implementing new functions, first do it the conservative way of reloading pages for every single change. If this is working, add the same functionality with Ajax. You will see that you can re-use some API functions if they are written well.