No and No. Version 6 will install as a completely separate program. Version 4 will still be there installed and untouched. You may uninstall 4 if you wish, but it's not necessary. Many of us like to keep the old version installed for a while just incase problems come up with the new version so we'll have something to fall back on to get the jobs done until the new version works right, or, more likely, we learn how to use the new version properly.