You can upgrade without big issue.
Use the zip file to upgrade VC (remenber to use the existing ODBC DSN to perform the upgrade).
Then upgrade VUM (but also the old can be used).
Finally use VUM to upgrade the hosts.
PS: if you plan to use View 4 remember that U5 is not supported.
Andre
Andrew | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro