It is up to you how involved you want to be into the game.
Any of the SH series can be both: very realistic, hard, complicated and simple point and shoot. It is up to you.
On some of your questions in regards to compatability and download areas I already answered in your original thread in another subsection of this forum.
I'm not sure what "bells & whistles" are, but there are lots of mods around here
I would agree with Segwin - you'll have to read a LOT; depending on what do you exactlyu expect from the game that is.
If modding and reading bother you - I would recommend playing a little bit as it is, learning the game as it is starting from scratch (no manual targetting) and going from there.
As you progress and read more about the mods and the game - at that time you can decide whether you want more or not.