If the new survey comes up with wet and cracked rudder issues, you could just factor a replacement into your offer. My rudder on the 310 annually accumulates a little water and my annual routine after hauling is to drill a small hole (3/16) at the lowest point to let it drain over the winter so it doesn't freeze and crack the rudder. Then in the spring, I just fill the hole with glass impregnated epoxy. I think that is a common issue with Beneteau rudders if I'm not mistaken. Sounds like yours was allowed to accumulate and freeze.