I normally wouldn't recommend doing that. Usually, I would use a DNS virtual name during the initial setup to point to the SQL server name. This would be useful if you decide to move off to a cluster or to another server.
If you really need to change the name, you can backup and restore the 14 databases to the new server and then re-run the configuration manager (run it for each K2 server node) to point it to the new DBs.
One note here, I recalled that I had to check the properties of service broker instances using the ServiceBroker management console (C:\Program Files\K2 BlackPearl\ServiceBroker\BrokerManagement.exe) to make sure that all instances were using the correction server name in the connection string.
As always before doing anything, you should do a full backup of all the server files and also the K2 databases. This will allow you to roll back if anything doesn't work.