Hey NF...
Check shower valve first...
Then, since the shower floor is firm...the wingtite drain may in fact work for you....if it didn't, then you would have had to open ceiling anyway. I say you have nothing to lose.
Check out this web site:
http://search.aol.com/aol/imageDetai...ower%2520drain Be sure to click on the installation instructions. They also have deatiled instructions on removing the old drain...pay particular attention to removing old drain becuase you can't make a mistake and cut the shower floor...
Also, you want to use any silicone that says it is mildew resistant...too many different kinds in each area. Just find one that is mildew resistant.
How long is the pipe from the old drain down to the ptrap under floor (stick tape measure down inside drain 'til it hits the trap)??
If long enough to do this, you will need an inside pipe cutter (see picture), a 2" ABS coupling, ABS cement and primer, a small piece of 2" ABS plastic pipe, and the wingtite shower drain and correct silicone.
I also recommend that you practice using the inside cutter by setting small piece of pipe in vise or similar and practicing straight cuts from inside the pipe...2" ABS coupling only has a 3/4" socket makeup at each side of coupling...so need to be good and straight.
Review info...let me know if need more information.
Mark