Have joined and paid to purchase Silent Service 1&2.Followed instructions and downloaded all additional content but not the game itself. Could someone please help with the downloading and installation. Cannot find game even after using downloader. HELP!

The installer is rather small, so you can easily download it directly in your browser, without GOG's downloader.
Go to your game shelf, deactivate the downloader and click on the installer to start the download (see screenshot). Your browser might ask you where to save the file, then choose a location or it'll automatically save it in your standard download folder.

If you don't find it afterwards, you could still search for the file. E.g. use the Windows search and search for setup_silent_service

To begin the installation on Windows, run this executable file:
setup_silent_service_2.0.0.7.exe
(the ".exe" part may be hidden on your system)

Let me know if you aren't using Windows.