Yes please!
Great!
One hopefully simple way is to make a diff -u and attach it to a trac ticket.
The better way would be to do a git clone of the webwml repo, and put it on github or whatever your favorite git hoster is, and then make a branch with various changes, and then I can pull down your repo, look at the branches, and merge them.
Should I be contacting each mirror owner, or just remove them from the list if the websites listed don't resolve or return an error?
I think fixing some bugs in the mirror checking script would be helpful too, if you want to go even further. For example, if you run the update-mirrors script, I think it rewrites every line for failed mirrors to be "number of hours away from UTC" hours later. That is, there's a time zone bug somewhere in the perl. I bet there are more too. :)
I will certainly look into this too, although I'll admit, my perl skills are lacking. However, I have been wanting to learn a new programming language, so if there isn't a huge rush, I'll tackle it.
Tyler