OK. Here is one of the most basic "repairs" that people who ride a lot have to learn to do. I put "repair" in quotes because is is a maintenance item which if left so long that it falls into the repair category you will have to learn to replace other components. Replacing a chain isn't difficult and can be accomplished with very few tools, in fact an experienced home mechanic will only need a chain tool, plus the knowledge about how to do it. As someone who used to ride as much as 16,000 km per year, I have changed many chains. If I had had to go to a bike shop every time, I would be much poorer now than I am