In terms of content not that much - just some small updates here and there. I don't think that any of the recommended lines changed.

The biggest change was undoubtedly the format of the book. The original book was one of the first (maybe the first?) quality chess did and used quite a small format while the updated edition moved to their now normal, much larger, format. 
(presumably this was a logical move when they needed to print some more copies of the first edition.).

The second edition is certainly a better read from an aesthetic point of view so worth getting, although probably not if you've got the first. If you don't then either edition is very worthwhile

yes its BTS 3. This was the  bibel back then. I would prefer Be2 vs. the
Najdorf and play like Geller 

no the book is from 1995. 6 f4 against Najdorf,6 g4 against theschveningen,9.0-0-0 against the dragon,6.Bg5 against the classical and 7 Bg5 against  the pelikan  so far he has succes at icc

Which version of Beating the Sicilian? Nunn did write 3 editions. I am assuming the first one written in 1984 (i think), which means either 6.f4 or 6.a4 vs the Najdorf, Keres attack or Be2 vs the Scheveningen, 6. Bg5 vs the Classical, and 9.g4 vs the Dragon. While theory has obviously developed, none of these lines have been refuted (If they have, let me know!) . Black may have clear paths to an equal game, but if White knows the lines, he should be fine. Plus, it gives him a good starting point from which to improve. If he loses, it is not likely due to the opening...

Always nice to see players returning to tournament action. Tell your friend good luck and welcome back!

My old friend is having his tournament comeback after a 10 years brake. 
He used to play the open sicilian with the white pieces and will play it again now  .
his bibel then was John Nunns book. "Beating the sicilian"
Imho i think his "crazy" he will get smashed. My advise was "play the colle" or somthing slow until he gets the hang again.

What do you guys think. hes was rated around 2000