I remember thinking at the time (guess I was in my very early teens)... how the heck do they play all the way through such complex songs and remember everything? I was trying to figure out... are they making it up as they're going along or did they actually write this?

My young brain couldn't comprehend that a bunch of young 'stoner' looking guys could be capable of having such talent.

btw: if you guys don't already.. and you're interested in the 'making of' aspect of music, I'd suggest getting an account at GigaNews and logging on to the alt.binaries.mp3 newsgroups. Like, seriously, I've been finding all kinds of amazing gems like all the early bootleg recordings of Pink Floyd etc. Plus stuff like Van Halen coming up with Eruption in the studio, Queen's basic backup tracks of stuff like Bohemian Rhapsody before the main vocal had been added. Every version of every song the Beatles recorded including the original camera audio feeds from the rooftop concert and arguments between them in the studio and jams, christmas tapes etc.
The original recordings of Stairway to Heaven with a completely different chorus.. early recordings of ELO and instrumental l edits of albums like New World Record.
I could go on but ya get the picture.
It's an amazing lesson in songwriting just listening to how different aspects of songs were dropped and changed or how early ideas sparked a song into a totally different direction.