is there any fixed gear specialty shops there in Denver?
I used Bicycle Village in Aurora (just S. of Denver, off Hampden) for a little help, as they maintain all my other bikes. There is a great tech there named Steve O. who provided the Surly spacers and cog that I needed, and helped me pick the gear ratio. He loves working on projects like this and made my project easy; I would recommend calling him with your questions, he is very enthusiastic about his work.
I also hear good things about Salvagetti’s in Denver. I believe they do a lot of fixie/single speed business.