Trident, yes that is basically how it works.
Essentially there are only three chords in a song, all others are variation, you can literally play most songs (allthough there are exceptions) with only three chords. The tonic, the dominant and the sub-dominant chord. The dominant chord is to right of the tonic (the key of the song), and the sub-dominant is to the left of the tonic, this makes the tonic, the dominant chord for the subdominant. As a basic rule of thumb, the dominant resolves to the tonic. And the subdominant resolves to the dominant. The minor chords on the oposite side is the paralel keys. Am is the paralel key of C, meaning the scale is the same for both keys. So essentially you can exchange any tonic chord for Am, the same goes for the subdominant, and the dominant.

Example: (key of C)

2-5-1 progression. This is by far the most common progression ever.
In the Key of C:

Dm - G - C

If we simplify this we get:

F - G - C
Or
Subdominant - Dominant - Tonic

Once you get this you can add stuff like 7ths, suses and stuff like that later... But get yourself a keyboard, or a guitar and learn the six chords of a key, then basically you can learn any song in that key.

Doc-Z