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If it came with a .blend file then you can open it and work on it in Blender, which is free. But, have you ever used Blender? It's a very powerful program that utilizes Add-ons to simplify and streamline the modeling process, so you will need to spend some time watching tutorials. I would recommend the Blender Guru's Youtube channel for beginner tutorials and then Ponte Ryuurui's Youtube channel, as well as Josh Gambrell's channel for more advanced tutorials.

You're welcomed. Re: edit vehicle. I don't know exactly as I don't work with printable 3D models although Blender, which is free I believe, can edit .stl files according to an Internet search.

Good point, I've edited mine above to this

If using accoreconsole and a script calling a lisp (tblsearch "LAYER" yourlayer) will return true or nil, so write dwg name to file, use the "A" option when opening the file to append the answer. Look into Accoreconsole. https://through-the-interface.typepad.com/through_the_interface/2012/02/the-autocad-2013-core-console.html