Setting up the guitar
It's a fingerstyle song in the key of C, in standard tuning, EADGBE.
What Fahey plays on the recording
To get started, this is a transcription of what Fahey plays; it's a bird's-eye view of the upcoming sections, delving into each move piece by piece.
the Opening Cmaj
The entire song is in the key of C, and Fahey starts with a C chord..
Only, it's not exactly a normal C-chord... it uses the 3rd fret of the low-E string (the 'G') note, in the bass, so it's a C/G chord.
the F chord
Next, this is the IV/F chord, which is then followed by the #IVdim / F# chord.
Note: the 6th string notes are played with the fretting-hand thumb wrapped around the neck
The first ending
To complete the A-section, there are 2 endings that Fahey plays.
For the 1st ending, he goes from II7-V7... D7-G7. These create a string of 'secondary dominants' as the D7 is the V7 for the G7 (which is then the V7 for the Cmaj upon completion of the ending); each chord leads into the next.
The second ending
On the second-go-through of the A-section, Fahey plays this II7-V7-I ending, which is D7-G7-Cmaj
For the 'main riff', that's it! What comes next are the 2-3 sections when Fahey breaks-away from the A-section. (For details about when those are, the full transcription above will show this.)
The bridge (first half)
For the 1st time the A-section's broken-away-from, Fahey plays the chord progression: IV-#IVdim-I/IV / F-F#dim-C/G.
This is the 1st half of it, then the 2nd half has a slightly different progression.
The bridge (second half)
It's still the B-section, and now the 2nd half of it. For this sequence, Fahey changes the chord progression, playing IV-IVmin-bVII-V7... F, Fmin, Bb7, G7
At the end of the chord progression, the V7/G7 helps to lead the music back into the Cmaj of the A-section
I, IV, and #IVdim chords (3rd time)
To finalize the C-section, Fahey keeps the same I-IV-#IV chord progression, but moves the treble notes into higher pitches.
After repeating this pattern a few times, Fahey then enters the D-section.
I, IV, and #IVdim chords (1st & 2nd time)
Between later A-sections in the song, Fahey plays this C-section (and D-section).
To begin the C-section, Fahey continues playing the Cmaj-Fmaj-F#dim / Imaj-IVmaj-#IVdim as he does in other sections, but it's plucked differently.
During the D-section, Fahey temporarily changes the tonic/root of the song into the 'relative minor'.. Amin <--> C
First, he plays an Amin barre (5th fret range)... and then moves back into open-position chords C->E7->Amin.. the G7 leads back into the Cmaj later
That's it as far as new parts for the song! Those are the pieces to play the song to completion.
Wrapping things up
Thanks for viewing this write-up/guide for the Assassination of Stefan Grossman, by John Aloysius Fahey.
PS: after Fahey wrote this song, Stefan Grossman 'retaliated' with 'the Assassination of John Fahey'. It's recounted in the documentary"In Search of Blind Joe Death: the Saga of John Fahey" (2013)