Conversions from one game to another tend to be easier if you have the original blender, Maya or 3DS MAX files to start from.
However, that can cause problems with attribution when you publish a mod. For example
this dress was adapted from a statue of Hebe mesh that Tamira also put into Oblivion/Skyrim as a static. I didn't work from
her mod, but from the original blender file that we both downloaded from a free 3D site. We each made changes to the texture, in my case adding transparency for the dress, and in hers adding foliage, as she'd put a plant in Hebe's cup. So the results were independent, but if you see both together, the common origin is obvious.
To further confuse matters, we had the same model, but got it from different sites, where the author's names differed.
I can't remember which one it was, but I had a complaint on one of my Oblivion mods that I'd stolen a mesh from another game. Which was partially true, as it was one of mine in that game, too, but a group effort without our individual names/handles.