You lucky dog. I love old machinery. Agree that the last thing you probably want to do is regrind the top. Old saws like that rarely need to be flattened, and the dings and patina just add to the whole package!
As for what it's worth? I have no idea if it has any value as a collectible, but I know utilitarian people who'd drop about 5 bills for good cast iron like that, maybe a little less if the motor was on its last legs or sumpin. And that's before they go spend a little more putting new tires, guides, etc on it. There may be those out there who'd spend more though, but I can't afford to hang out with 'em.
Enjoy that thing. It'll make some good bows.