If you yank the whole sink out it's much easier to get the old faucet off and the new one on. Although a
basin wrench might get it, the nut itself isn't rusty. I use a basin wrench so seldom I usually can't find it and have to buy another, so I must have a bunch of them somewhere in the garage, or attic, or one of the storerooms... or maybe I lent it to Pablo (who gets blamed for everything).