Bathtub drain help

Ok, so in our bathroom we have one of those crappy one piece fiberglass installed bathtub/shower. The house is about 12y/o and I was cleaning it the other day. Well it was kinda soap scummy so I used a soap scum remover, I guess it is an acid based cleaner. Because it pitted the drain all up. It is one of those twist to close twist to open drains like this




Is there any way to recoat this thing to fix the pitting in the metal? Or is there a way to replace the drain without removing the whole buthtub/shower?

I've only pulled one tub in my life...You don't want to waste your time recoating it, it will cost more then a new drain. You maybe (check before you do) be able to cut the chalking out from around the drain, then pull it that way. I believe thats what you need to do, but don't take my word for it