I have a 2000 Civic Si. My car has been starting to backfire a little lately. I'm pretty sure that means i'm gonna need to adjust my valves and timing. My car has just hit 75000 miles, the manual says you should do this at this time but the honda dealership says I should wait a while. Does anyone know how much it usually costs to change a timing belt and adjust valves? Can adjusting valves be done by anyone with a little guidance or instruction? If so how?