I currently have RU mini license. The pro license was recently purchased and I have the new key. Do I have to do a new install to make this upgrade or can I just change the key information in my current setup?
No need to re-install Remote Utilities. Simply add your new license key to the License Key Storage as described in this registration guide. Before adding the new license key (the PRO one) please make sure to select the previous key (MINI) in "Available keys" list and then click Remove selected key - this way you'll be able to add the new one to the keys storage.