2001 Honda Civic timing belt

I have a 2001 honda civic it started making a quiet knocking sound about 2 weeks ago listened real carefully and felt a tapping coming from number one injector I thought it might have a slight clog putting back pressure on it so I filled the tank and mixed a bottle of fuel injector cleaner like the directions said drove fine for the frist 30 miles then started knocking even louder. So I started to limp it home and it lost all power and died. I turned it over it started but it was running really rough like fouled spark plugs or out of timing. What do you guys think? If its the timing belt how hard and how long is it to change thenk you for your time