I’ve finally read up and watched enough about rear end diff work that if I was not already swamped with projects and needed an axle, I would get a clothespin (gear oil stinks, even new), and go at it on a second rear end that was not obviously bad. But since you have a lead on a good mechanic who will do it right for a good price, no one is going to blame you for having it done right the first time.
