Stay away from Worst Buy if you want a decent antenna. Most of what they have is junk, and the few items they carry that do work well are horribly overpriced. Radio Shack stores now carry antennas and equipment made by Winegard, which has had a good reputation for many years, but again, they charge a lot. You can save quite a bit by buying online, even with the shipping charges.
As for installers, there are still a few around. Go to dexknows.com and search on "antennas" in "Denver metro." I found several that way. (No, I'm not one of them. )