How to replace o-rings in fuel return lines?

To replace O-rings in fuel return lines, first, ensure the fuel system is depressurized by removing the fuel pump fuse and starting the engine until it stalls. Once the system is depressurized, disconnect the fuel return line carefully, using appropriate tools to avoid damage. Remove the old O-rings and clean the sealing surfaces thoroughly, then install new O-rings, lubricating them lightly with clean oil to ensure a proper seal. Reconnect the fuel line, reinsert the fuse, and check for leaks upon re-pressurizing the system.