Hello,
The 7.4 version is the latest, there is only one hotfix and yes you can upgrade to 7.4 . The installer will see the previous version and can complain about the SQL versino if you use a 2008 SQL remote server. It will update the binaries and update the database shema. There is an issue with updating and reports you can use from SIM but if you don't use that function you should be ok !
