Classes are definitely recommended, one on one or classroom would depend on your learning style as well as what you can afford.
At a minimum, you will want a holster, eye protection, ear protection, and cleaning supplies. For a Glock, you can use the provided brush, and some cleaner like Breakfree CLE or Hoppes.
Glocks field strip into 4 pieces, all of them are easy to clean. My 6 yo can reassemble it. Other handguns can be harder.
Under federal law, you have to be 21 to purchase a handgun from a FFL. You have to be 18 to purchase it in a private sale. There are no federal laws specifying a minimum age to carry, so there is no concern there. I can't speak to CO's statutes.
I'm sure that there are written guides to etiquette, you can probably google that. But at the range the RSO (Range Safety Officer) will be happy to go over them with you. You should talk to the RSO anytime you visit a new range, just so you know the rules (unless they're posted.
Learn the 4 rules of firearm safety well, as well as how to apply them:
http://en.wikipedia.org/wiki/Jeff_Co...irearms_safety