Just got my service working, and able to install it with a normal .msi installer. Oh happy days :-)
During installation of the service you will get a question which user you want to run it as, choose the same user as you used when running the GUI.
Why? Well because when configuring the repository database connection in the GUI, that information is saved in the users register, and as long as you’re on the same computer the service will automatically pick it up and connect.
From the GUI you can change if you want to use the GUI or the service to collect meta information, just start the GUI and go to Settings, Collection and check or uncheck the box at “Use Windows service?” See picture below.