What part of "stay out of the finder" do you not understand? iPhoto organizes photos in its own way so that it can find them for you. DO NOT RENAME FILES IN FINDER! Do your renaming, organizing,etc.from within the app and you will be fine. All dates will be preserved, etc. Windows makes the user work entirely too hard in having to rename files. Let go of your windows ways and let the app do the work for you -- that is why it exists! You should have a backup of the iPhoto library (you do, don't you?), so put that back and then stay out of the finder. all will be back to normal.
If you don't have a backup, I'm afraid you are sunk. You obviously did not listen to the advice given several times over in this thread about naming, exporting, etc.