I would highly recommend to replace with a new tub/shower unit, remodeler unit comes in three pieces and you can carry through a standard door. Your old unit is four years old which means the faucet and drain is also that old. Change it with a good quality unit. Go to a plumbing supply house and not your local Menards or Home Depot. You get what you pay for.
Be prepared to find the floor near the tub rotten and definitely replace whatever needs to be. I’ve been in business 33 years and would never think of trying to repair or re-color a 40-year-old unit. Foolish.
Sorry for my blunt answer but that’s how I talk to my customers, they ask my opinion and they always get the truth