I just did a quick google search for "denver retouching studios" and got this link: http://squarepixels.com/
My advice would be to find all of the studios like this in the city, and all of the advertising agencies, and maybe even some of the busier photography studios and offer to intern. You'll likely learn more usable information and technique that way. School is good, don't get me wrong. But in my experience, the photoshop and retouching classes I had in college in no way prepared me for real world professional scenarios. What art school gave me was a connection and a foot in the door. A very expensive foot in the door.
The downside to an internship is that it might not pay well, if at all. I think if I were entering the field now, as opposed to ten years ago, I'd rather have a non-paying internship that offers "real" training than spend a ton of money and not really know anything afterward.