I have not taken the tub liner out yet but am having a difficult time removing the drain. Do I tear the liner out first or somehow unscrew the drain. This appears to be a 32 x 48 liner. The walls are tile above the liner.

Roger, I think you may be describing a fabricated shower pan floor and not just a liner. To be sure tell us more or post a picture. A liner would have to be lining some previous fixture.