It is a JOB. A couple of suggestions… while you’re at it replace the waste and overflow and if possible the tub/shower faucet. Second, you can get tub surrounds in two pieces that will fit through doors and three (I like the Sterling brand surrounds), American Standard makes an Americast tub that has the properties of a cast iron – but without the weight. I personally prefer Kohler cast iron over Americast as I think it’s more durable. By the way, you can break out the old cast tub with a sledge hammer and cut up a metal tub with a Sawzall.