One of our sons had to go to the ER in an ambulance today (he'll be ok when his head unfogs, it appears). Is in his 20s, and lives hours away from us. He lives with long time GF. Concussion from auto accident. Took a long time to get the ER staff to deal with GF as "family" (and, legally, it was probably not appropriate).
He (and other kids) were supposed to have taken care of this, but he had neglected it: "Hey, I'm a mid-20-something male, an athlete, in great shape, and a grad student, so no need for that old people BS" is the imagined interior dialog. :-)
Would have been much easier for him and her if this had been done. Plus, if the ER staff had insisted on strict compliance with the law, no one could have stepped in for him. (Remember, if you are over 18, in most states your parent(s) legally can't direct the healthcare if you are unconscious or whacked out).
It is a simple document, and I suspect that Nolo's forms will probably work.
http://www.nolo.com/legal-encyclopedia/living-willsThis is one of the situations that a little work up front will pay monster dividends if you happen to get hit by the proverbial truck.