One of the processors in my Dual 2 GHz G5 died this past weekend. My machine was purchased in fall of 2003. I am currently running on one processor . . . I'm guessing it'd be ridiculously expensive to have apple fix it.
There are apparently two revisions for the Dual G5 -- I have no clue which one mine is, but I'd assume I have the older version. My serial number starts with: XB342 meaning, 2003, 42nd week.
No idea what these things are going for. welovemacs.com has them for like $589 brand new, but even that seems waaaay to expensive for a defunct processor.