The drain unscrews from the assembly below the tub. Normally the drain and overflow are all one assembly. If you have access to the back/underside of the tub it's a lot easier, because you can control both the drain basket from the top and the nut that captures the threads on the basket from below.

However, you can try to replace the basket just using access from above. Easiest way is with a tool called a "basket wrench":

An inexpensive basket wrench costs maybe $5 to $10 at a hardware store.

You can see how this would lock on to the cross pieces in the basket and allow you to rotate the basket counterclockwise to unthread it.

Or you can use the standard DIY method which is to insert two sturdy screwdrivers into the basket, one at the 9 o'clock position and one in the 3 o'clock position, and cross the screwdrivers and use that leverage to rotate the basket.

Once the basket is removed, clean the tub surface and install a new basket using a bead of plumbers putty.

I will say that the proper way, and the best way, is to have access from below. It's best to set the basket into the putty and then secure it by rotating the nut from below instead of rotating the basket from above.

thanks mongoct,
It's on the second floor with no access from below and of course it wasn't installed with the drain end of the tub facing the linen closet.
I'll have to try and get with a basket wrench from above.
thanks again

That is one of many wrenches available for removing this fitting (there are more with different teeth designs). I own a few different types but don't like to do this type of repair as the down side risks are so great (poor connection - flood your lower level). If you live in a Condo or multi family housing home have a plumber do this for you - they carry tons of insurance liabilty.

It's crazy talk in my opinion to do this replacement without viewing the connection from below. The old plumber could have siliconed the fitting, used plumbers putty and or a good rubber O ring. We have inspection cameras that could get in and look - but it's always better to look and feel first hand.

Once the the fitting is replaced fill the tub and drain it at least 5 - 10 times. Look for moisture and when your satisfied it's top notch - repair the ceiling patch from below.

Good Luck.

I feel your pain! I solved the same kind of issue with some chrome paint and a Flip-it drain stopper.

Our drain is pretty old and the ring of the drain flange that shows once the stopper is in place is less than 1/4''.

It's the cheap and cheerful solution to something that was starting to sound like potentially having to gut the bathroom!

Here is a link that might be useful: Flip-it Drain Stopper

Thank everyone for your help.
galleyette what kind of chrome paint did you use and where did you get it?