Oduodu,
What has been said is helpful, but to my mind parts of the end result. Musical enjoyment is essentially the end goal, but you specifically asked on how to become 'hi-fi wise'. I take it that would refer to equipment, not just the realisation of what is important.
Not sure of where you are at present (I mean background-wise). You will really have to have some hardware background, as in know what a transistor is, what an amplifier and the other periferals, and very basically how they work. That does not mean you should become a design engineer, but questions and (worse) misunderstandings will periodically crop up if this background does not exist.
Now we can come to the 'where' - sadly I do not know of one single source. I would presume something starting at the basics should exist on the internet. The advice re Wikipedia is helpful. As RS4 asked, where are you?