I have been trying to make my own items... It seems I cannot find the Model, Inventory Image, and Message Icon for some reason, and it is impossible to cut and paste for this (don't know why it was made that way) and I was wondering, where are the item models, etc.? Also the files downloaded to my OPAL folder do not appear... even the folder itself says its empty, but when I try to download them again, they are there with a little lock next to the icon... WTF is goin on with GECK??? Please Help.
If you're just making a new version of the same thing (for example, a gun that looks like the 10mm but does different damage) or otherwise want to re-use some thing from a pre-existing item with slight modifications, you can double click on the item in the object window to bring up that object's window. Then change the Object ID to something unique, and make any other changes you want. Then click "Ok" and when it asks if you want to create a new form, click yes.
As for where those assets are located, they can be found in your .bsa's, and can be extracted from said .bsa's with a program like http://geck.gamesas.com/index.php/FO3_Archive
Regarding the files downloaded to your OPAL folder, I'm not sure. A little lock next to the icon sounds like you have something in place that's trying to protect you from those files, maybe? Also, it may be a dumb question, but are you absolutely certain you are downloading them into that folder? In any case, its not the GECK that's doing it.