Don't delete carrara. Do make sure you have the new demo w/ patch.If you need to just install over the older demo will not hurt anything, uninstalling might kill the demo. Need to know more about how you are bringing it in. There is native and transposer2. Is it an obj or pz3? Often you will have to manually apply the textures if it doesn't pick them up like with obj that doesn't get a mtl file or c can't find it because of a path issue. The master shader message is no big deal and is very generic and common when you go to alter a shader.It should be able to bring things in fine for the most part with a proper pz3 or obj file.

No need to think outside the box....
    Just make it invisible.