Our irrigation is knocking and I have been told by 2 companies that a valve needs to be replaced. I have a rainbird system and I am fairly handy, but have not had to do any more then replace sprinkler heads. The quotes we're 125.00-160.00 per head to replace and during the times in which we live in, I would like to save the cost if this is something easy to do myself. Does anyone know of a website that I can go to to show me step by step to replace this valve. In box # 1 two valves are attached,...