Thank you for your questions.
So I am wondering, is it possible to run the Agent simultaneously with the Host?
No, the Agent won't be running simultaneously with the Host. However, you don't necessarily have to have the remote user uninstall the Host. They can simply stop Host using the right-click menu ("Stop Host" item). Once the Host has been stopped, they can run the Agent.
Note that the Agent will have different access credentials and other settings than the Host because the two programs keep their settings in registry entries/keys and can co-exist on the same computer.
If no, what would be the recommended best practices for walking a user through granting access through a Host without disturbing the existing configuration (assuming they are already using Single Password)?
If they need to change authorization settings for the installed Host, they must run "Settings for Host" and navigate to Authorization:
There are different ways to access the Host settings:
1. Right click on the running Host icon in the system tray and select "Settings for Host".
2. Windows Start menu -> Remote Utilities Host -> Settings for Host.
3. Using command line option
: rutserv.exe /config
With the last two options you can open the settings without the Host service actively running.
Hope that helps.