Is blender the only program I can use to make vehicles? I don't like the way blender is set up, but it's the only program I see people use for vehicle creation.
If you're not willing to pay money for the tools you want, Blender is your best bet. Google sketchup is a mess. Only a handful of users on the forums that I know of know a workflow for Google sketchup that works for them. Its a chore to make anything that would be usable in BeamNG with sketchup, and when I was last using it, I had to deal with so many issues that I simply would not have to deal with if I was using Blender. Also the warehouse models are a pain to deal with if you want to export them... However this is generally seen as a no no in the community, even with permission to use assets, so I don't advise you try it to make something you plan on releasing. Watch a few tutorials regarding vehicle modeling in blender. Learn the basic tools you need to know to get started, and then try something. This is how I got started, and I have certainly gotten more used to Blender than before. There is alot of stuff crammed into blender. It is a very powerful free tool, if you just know where to get started.