If I understand you right, you renamed all of your textures into "myLevel". That is good so, and there should be no problems with missing textures, if you have a problem with the old texture not deleteing from the level, just retexture it with some other texture (make sure you select the wall, and then press "shift B" to select the whole brush), rebuild all save your map and then restart the editor. Now you should be able to get rid of the old texture.
To Carnage, yes we would need all the textures and sound and whatever, but as long as it is saved in the package, myLevel, it is automatically saved witht the map.
