I have a 1960 home and the bathroom has wire mesh, 1" thick mortar tiled shower walls and ceiling with a plastic shower pan. There is a leak and I want to gut the tiled area and replace the pan. #1 what is the best (easiest) way the do this. #2 can I remove just the shower area without messing with the rest of the tiled walls in the bathroom?

As an option, is there any to just replace the shower pan without tearing the walls completely out?