If I want to mod automation, but have absolutely no Idea how to use 3ds max, should I get it anyways?
Nothing preventing you from learning how to use it 
Someone on the forum needs to make a really dumbed down tutorial series for newbies in which they explain what various useful tools do, because when I tried to learn it I couldn’t find any such videos and gave up pretty quickly.
Autodesk has some pretty good tutorials on their website.
docs.autodesk.com/3DSMAX/16/ENU/ … index.html
The airplane tutorial is, IMHO, fairly good to learn how to make stuff for automation.
For the game specific info, Andrew’s tutorials should get you fairly far.
Yes, you only need extra patience 
And of course, to watch some tutorials. Youtube, autodesk forums and wiki are all you need to learn 
Another question. Can I convert Blender files to 3ds max?
I think you can… But I don’t know if the file will be usable for an automation mod. I think is better to spend a few hours learning how to use 3ds that an hour converting files every time you model something.
EDIT: if you can’t wait you can learn by doing the mod itself… this is a good tutorial for modeling a car 3dtotal.com/team/Tutorials/f … 00_m01.php
You would probably be able to do the mesh itself in Blender and convert no issue, but unless you are already a pro in Blender I would recommend using 3DS Max all the way.