Well, the good news is that they didn't either forget to put in *any* new oil or forget to torque the drainplug -- classics that tend to have prompt and unambiguous symptoms.
That's also the bad news.
If this happened as you describe, I think what's fair is that the dealer should take care of any engine repairs needed.
Whether you *get* that, at least as a prompt solution, depends. Driving 400 miles and adding three quarts of your own oil muddied the waters more than a little, and sometimes you have to fight hard to get your due in these scenarios even when the evidence is very clear.
I'd say, first give the problem a chance to be easy. Talk to the service manager. Maybe he'll be a good sport about fixing your engine and there'll be an all-hands meeting about quality control too.
If *that* doesn't work, your choices are to escalate all the way to an attorney or to go to the consumer-affairs desks at one or more of Denver's media outlets. Sometimes their negotiating skills and the implied threat of bad publicity can get you some satisfactory results without the adversarial proceeding (and likelihood of out-of-pocket, up-front costs) that you get in a law office.
However, just consulting a lawyer is inexpensive and useful in getting a clear idea of what you do and don't have going for you. Be sure to get one with a specialty or at least some experience in consumer affairs -- lawyers come in many kinds, and getting the wrong one can be like getting heart surgery from a podiatrist (or foot surgery from a cardiologist).
Whatever course of action you choose, do take one! Everybody makes mistakes. The good businesses apologize, or at least give you the benefit of the doubt, and set it right. The bad ones hope you'll roll over for it. You're about to learn which kind has been fixing your car.
Best of luck,
--Joe