New Post: Restarting Windows service and conditional launch

I have a Windows service which I install and start using WixSharp. This works fine. The service is extensible in that additional functionality can be registered with it through another WixSharp installer (it drops a config file and an assembly for the service to pick up). I need some guidance on two questions:

1. Following the second install, how would I restart the running service so the additional functionality can be picked up.
2. What would be the recommended approach for a launch condition the makes sure the Windows service has been previously installed?
   

Thanks,

Jim