I agree it looks like a plastic end tank and if I were you, yes I would for sure 100% replace it asap. And then get ready to start replacing all the radiator hoses, I'd also do a thermostat and probably a water pump and timing belt components along with the all seals behind the belt on the car, spark plugs, wires, oil, filter and change all the other fluids. Trans, t-case, rear end, clutch fluid, brake fluid. Just freshen things up, the car will be happy and you will be happy with how it runs and how much longer it will last for you.