In that case, I'm guessing your entire drain setup is plastic. I once pulled out a shower drain on a '93 2251 and it is all plastic, held into the bottom of the tub/shower with a plastic ring/nut on the bottom and sealed with putty tape under the top lip. Since it's all plastic, it very well could split, but it also could be the putty tape is starting to leak. I'm not sure if there is a good way to pull out the shower, because that shower/tub I mentioned above was already removed to make room for a shelving unit. I wouldn't let it go too long because the floor will start to rot, and then you'll have a really big mess on your hands. I'm not 100% familiar with your coach, but I do believe you might be able to access the drain from the exterior storage compartment, or an interior wall if there's a removable access panel.
Jon