Unhappy [Q] Updating GT-7100 v.4.1.2

This might come as late issue, since everybody already moved to 4.3 or 4.4.2, but the thing is I got stuck from my own insecurity to install a Custom Rom, and standing behind is starting to hurt my device.

Since it's rooted, I cannot update automatically trought Kies, but I just don't get to understand all the variables implied on flashing or installing a Custom Rom, from bootloaders, Knox, constantly appearing new versions of required software, hipertextual installation guides whose requirements link you to either obsolete utilities, or utilities for which my device became obsolete, and seas of prerrequisites whose end I cannot manage to find.

So, I would like to know if there's any short way for getting out 4.1.2. Would TriangleAway help me?