PeterH,
You may be surprised how easy it is once you have got your head around the basic concept.
This really helps to not to fear to give it a try yet before reading the control theory book, thanks 
Could you please point me to any tutorial/example project, where I can implement any simple movement (a line follower, or any other thing) isolated from my own project, toward known, target results (already achieved by the tutorial / example project) to develop some skill?
I have already tried "Arduino PID" on google and there lots of examples, but getting direction from you is the point.