The new version has changed the multiplayer mode. Therefore, if you are developing competitive multiplayer, then do not update to the new version, you should wait for the Advanced Multiplayer add-on to be released.
Also, if you didn't work much with the 1.6.5 version, then it's better to install the new 1.7 release into an empty project.
But if you've already done a lot of work in the 1.6.5 release, follow these steps:
Delete all USK tools, leaving only the following folders and your things