Well, I'm gave it a shot with my blog. The implementation turned out to be easy enough, and you only have to link back from Profiles to a given domain once, rather than for every article. It also turns out there's a check box when you edit the profile that will allow you to hide your profile from search engines if you get sick of it showing up #1.
Ignoring blog posts, I doubt I've generated 300 pages of content in fifteen years, so it would only take a few hours to manually stick the tag in them all. Maybe next week.
Of course, when you use the Google verification tool, it complains that you haven't added all the possible parameters to the tag, like when the article was written, a titles, etc. That would take many days.