Just a few thoughts of my own, but if I were you and you got a 'fill in the form' kind of paper at your seminar, I would take it to an attorney and ask them what they charge to prepare the same. If what you received was just a list of things to think about and consider that's another story.
You will pay more for an attorney than using a form out of a book, but you will also have the peace of mind that it is written, signed, and witnessed/notarized properly and truly says what you want it to say. The attorney can also explain the documents and options to you if necessary so you can be sure of that. I've seen people with do it yourself Advance Directives where you simply check a few boxes to tailor it to your wishes. But that becomes a problem when you mistakenly check multiple boxes which turn out to be in conflict with each other.
As for copies, most medical facilities will accept a photocopy and treat it just like an original. So if you are tech savvy enough to do it, scan your Directive after it is signed and put it on a flash drive to keep in your purse, keychain, or car glove compartment. That way - if you are ever in a situation where you have to be treated or hospitalized away from your normal medical provider (who you should already have given a hard copy) - you or your agent can give the flash drive to the appropriate person to print off a copy of the scanned document for their file.
Again, it may be more expensive to do this, but something this important is worth paying someone to have it done right.