I have not personally owned a Grady White, but I have fished them and can say that they have a well deserved reputation as a great boat. I can't remember the model off hand, but I know it was a 25 footer and handled the water like a champ.
Having said that, 35 year old boats that haven't been taken care of aren't worth much besidespecially a good design.
My two cents... Good luck.