From what I've heard about blender, and also from my own experience, it's a better idea to spend a few quid on Zmod3!
Blender is free but Im not familiar with the interface....
ETS2 will give support on a future plug-in so users can use blender for modding SCS games...
However, just like Max I also use zmod, simply because it's better (interface, functions etc)
It however costs money, and you have to pay a monthly subscription.
Nope maps are created with the in-build editor.
Models etc (so mesh objects) are made in 3d programs but blender and zmodeler3 are the only ones who can export the object to the correct ETS2 files.