I am not an attorney. I do not know which form is legal in your state, or in the state that you vacation in (as they may be different). I encourage you to confirm your own situation.
We will start with the term Living Will.
According to Wikipedia a Living Will may also be called an Advance Directive, an Advance Decision, or a Health Care Directive and is the oldest form. Basically this is a statement of your instructions specifying what actions you would like taken in your healthcare once you are no longer able to make those decisions due to illness or incapacity. (Please note that this may not include becoming mentally incapacitated.) This form is effective as long as you remain alive, and should not take the place of your "Last Will and Testament."
A Living Will (Health Care Directive) does NOT appoint another person to make those decisions for you.
This link takes you to one of many sites where you can write your own Living Will for free. There are many sites out there, and most seem to charge a nominal fee.