Notepad++ and Blender 2.79 along with the plugins for Blender are the only things you really need for modding.
Ok thanks for the help guysHi JTGHD,
If you genuinely want to learn and have the patience, the information is all there in the Docs section
It also depends on what you mean by modding, whether you mean modifying the vehicle's characteristics such as engine, suspension or modifying the looks of a vehicle (skins, meshes), or just installing add-ons for vehicles.
If you're not already familiar, a good place to start is getting familiar with the truck file format
If I may be honest, it's a lot to read, but some of it is also interesting.