First let me say I'm not a plumber or tub refinisher, just a homeowner who asked a simalar question. What I learned was; there are people who refinish tubs/showers for a living and depending on what the tub is made of (I'm guessing fiberglass) will cost between $300 and $500. Another alternative (if you're a do-it-your-selfer)would be to go to Home Depot and buy some special paint (Klenk's Aqua something, I think) for around $20. and spend a weekend or 2 doing it yourself.

Again, I'm not offering advice, just posting what I learned.

Regards, Rick