No. Version 4 will update your Version 3. By the way, Version 4 also contains all the necessary files to install as a stand alone in the future, but if you have Version 3 already installed, go ahead and install Version 4 on top of your Version 3, i.e. do not uninstall anything first. (Your Version 4 will install into the same folder containing your Version 3, so that you don't lose anything.)
