Thanks for the post.

Managing ITIL implementation is very similar to managing any other project. It starts with a well defined scope.

There is no rule or norm that says yes or if you must implement the entire ITIL model at once. To obtain results, it is necessary to apply changes in stages.

Again, this needs to be defined within the scope and plan. Organizations approach ITIL with "an all or nothing" mentality. They try to implment all the processes when they are not necessarily needed or manageable. This is especially true for smaller business.