Oh dear, that is rather unfortunate. It would have been nice to have some of the older stuff to mod in NV.
You can use anything you like from FO3 for your own use, you just can't publish all of it. I think I'm talking mostly about meshes and textures and objects in general. Of course you could create a new mesh to replace one from FO3 and new textures to replace those from FO3, but you need to be very careful that none of that is just a copy of an FO3 asset even if it's a somewhat modified copy.
I needed a FO3 texture that was not ported over to FNV. I did just copy the texture from FO3 to FNV but only for my own use. A new substantially different texture will need to be created if I intended to publish. In this case it's a FO3 Mod transplanted to FNV, just that one texture is missing in FNV, everything else is already in FNV.
Well does anyone else know why my Rendering Window is not showing up? I think I may need it to use GECK. = 3=)""
You may have accidentally moved the window off-screen or changed its size so you can't see it.
Go to your FNV savegame folder, there are two ini files there: GECKCustom and GECKPrefs. GECKPrefs has a setting for the render window dimensions and position. For example:
Render Window X=1069
Render Window Y=73
Render Window W=715
Render Window H=586
You can change them if they seem wrong to you, don't just copy the above settings because they might not be proper for your display.
The official recommendation is to delete both ini files and run the GECK again, it will create new files. Just rename the old ini files to something like GECKCustom.bak and GECKPrefs.bak instead of deleting them so you don't completely loose them. If all is well then you can delete the backup ini files.