Script for changing all admin and VNC passwords

I do not have a script yet, but you can programmatically updated the TightVNC Registry entry to alter the VNC Server password. You can deploy this as a RSP Package using WDM or WMS Pro. An alternate method, or if you are using WMS Standard, you can deploy an updated version of TightVNC and provide the argument specifying a new password. 

For user accounts, run CMD "net user ". Make sure that the new password meets minimum password requirements for the OS or alter this configuration policy beforehand.