Installing one scenery will not remove any other scenery. Look for a redme file that usually comes with most addon scenery make sure it does not have any instructions in it with exclude switches. It will tell you where to put them. If you do not find any info on this then you will have to make them yourself. This is not extremely hard but rather long to explain here. If you look through the posts here you should find some info on how to do this.Other wise there is no other easy way to do what you want. As the only other way is one you do not even want to think about.