I still use a scope from one of my grandfather's guns, it's an old 6 power Weaver fixed scope with a chip in the eyepiece. It's at least 45 years old and it has never fogged up or lost zero. They don't make them like that anymore.

As for the rifle, I would leave her just as she is (with a new scope) and do upkeep as needed. My grandpa was the sort to use rustoleum on anything, so I just use the gun anyway I want. All he would care about is the gun earning it's keep. Enjoy your weapon!