Is there a way to edit an existing mod? I've tried doing some copy/paste/covert stuff and I get stuck on the texture part of the vehicle. I just can't get all the texture to work and i'm geeting erros. Is there a faster way of uploading a mod to the editor?

Quote from Hatchi :

Is there a way to edit an existing mod?

Yes - ask the mod creator to supply original archive file for editing. And if the creator does not supply it,you should not be editing it then.
Note that some mods have these archive files already in mod's page - look for download button under "Derivatives are allowed : YES" (no download button if "NO")

As an example of what Eclipsed said: https://www.lfs.net/files/vehmods/C52608

See down at the bottom right, there is a blue button "Download original archive"

For mods that have textures, the archives downloaded from this location actually contain png files so can be used in the editor.