hi, I have a v755 neovane pump, it was the original one that was on the boat, I am in the process of changing the impeller out and I started thinking I should completely tear it down and replace everything, it sat on the old motor in the elements since 1986 without being used, I have never taken one apart and im wondering if its just a bearing inside that I need to replace? im not even sure if I need to totally take it apart or just replace the impeller? and if I need to replace everything where do I get a gasket kit? I have the gasket to change the impeller but I don't have the gasket that fits between the two halves of the body? if the pump turns free I thought maybe just replace the impeller?