For the beginning part:

by measure:

G| F| Bb|C
Im going mental; Im going mental, etc...

Verse:
C|D|F|G
Repeat that while Joey sings the verse.

Now, in between verses, Joey will sometimes sing
Mennnnnn-tall, Mennnnnn-tall

On the part where he goes Mennnnnn, the chord you want is an A.  On the part  
where he goes -tall, you want to play a Bb.

Of course these are all power chords (root, fifth, and octave)