I have a fitted bath/shower, no access panel to the drain. The visible flange on the drain is corroded and unsightly. I had a plumber out to my house for a leak elsewhere, and asked him if he could replace the drain. He said no, it was not possible, because without cutting a hole in my kitchen ceiling, he could not guarantee that the shoe fitting would not drop and he would be unable to screw in the new drain and stopper assembly.
Question -- was he full of it? It seems to me that if this were a common problem, someone would have invented a handy tool which would allow the shoe fitting to be held close while the new drain was installed. If they haven't then maybe this is an opportunity for someone.
What he may have been worried about is if the shoe actually were to become disconnected from the sanitary tee. Yes, you can remove the old drain using a castle wrench (available from your hardware store for about $15) but, you do take the risk that if the shoe is corroded as well, or not tightly fitted, it might come loose from the tee and then you have a problem. I have run into some drains that have corroded and become seized to the tub itself and have to be 'tapped out' or even cut with a sawzall. Not a problem for me, because the tub and drain is coming out anyway. In your case, it sounds like if you encounter this problem you'll have to cut an access hole in your kitchen ceiling to repair the drain.