Car metaphors are tempting, but Yahoo vs. a startup is more like the difference between fixing up a rusty EOL aircraft carrier and building a sailboat.
I'm not sure the analogy stretches quite that far. Do you really care how many percent you own if you can drive it whenever you like and modify it however you please?
So you can dredge it up, and perhaps restore it to it's original glory...or you can go out and build your own, new dream car from scratch.
Either way it's going to be a TON of work to get to a truly valuable (and fun to drive) vehicle...