Thanks, everybody. I'm perfectly happy with the bike (frame and forks made in the USA!), but don't know where to start. I'm pretty good with my hands, but I get overwhelmed by all of the parts choices/sizes, etc. I'd like to repair it myself if I can. I can do tires/tubes, I have a chain tool (although now I am using an SRAM with the quick-release link), but have never tackled this job.

So I gather that I can just take off the chainrings and cassette and replace them? What do I need to consider as far as making sure I get the correct parts? I'm guessing I can take off the chainrings with an allen wrench. What do I need for the cassette? I don't mind buying quality tools if I think I'd use them more than a couple of times in my lifetime.