If I uninstalled Viber and then re-installed, will there be a notification to my contacts that I did re-installation (like when you first get Viber and it tells other Viber users who have your number that you joined)?
No, uninstalling Viber does not notify other people. It will only tell them when you last visited the application and logged in. If you don't log anymore, the application will display last time when you were online.