We have decided to replace the shower base in our bathroom but my husband is having trouble removing the old base to replace it with the new. There doesn't seem to be any screw or nails in the base or around the drainpipe. We think the drainpipe is secured to the base but we can't be sure. There are 4 small holes in the area surrounding the pipe plus that same area seems to be filled with some pliable but not removable stuff. Is there a trick to getting this base out??? Our house is 29 years old and I'm sure this is the original shower base. Please help if you can. Thanks!