You will need the Game archive extractor that SCS Software kindly made available on their website here. This is required to extract the base.scs file and def.scs file contents that are used to make all mods.
Secondly, if you plan to release your mods publicly, always keep your game up to date. Steam will update automatically, but digital/DVD versions will need to update manually from SCS’s site here.
If you don’t have Photoshop and the NVIDIA plugin you will also need DXTBmp. (When using DXTBmp open the dds file by dragging it into the program, click file>save as and save as a TARGA with Alpha. While the alpha channels aren’t important for the trailers, they are important for the company logo. After editing and saving your TGA, drag the TGA file into DXTBmp save as DDS.)
If you want to convert from game format (pmg/pmd) to Blender Tools format (PIM/PIT) you will also need ConverterPIX. cPIX is a user created program, however there may be plans to include it in Blender Tools in the future.
The MAT template can be found here
The truck templates can be found on the main ATS and ETS2 pages.