This isn't a flame- but I have a pretty good feeling on why you can't get any help from your dealer or Triumph. I am amazed you have gotten as much help as you have here, but nevermind that.
If you have access to the internet, there is no reason you couldn't find any info you were looking for, or find a dealer that would take care of you. Did you really believe there was not a factory service manual available? Do you not have an owner's manual? Why would you start working on the bike without any kind of reference material?
How have you confirmed it is a burned exhaust valve? And what was the cause?
One last bit - if your going to sell the bike - return it to stock as much as possible, sell off the accessories, and then sell it - you'll get the best return that way. Good luck with whatever you do.
