If I rebuild a Windows Service after making changes, can I just copy and replace the old assembly / .exe files to get those changes to run or do I need to re-install the service? Also do I have to first uninstall the service before installing the new version?
You don't have to uninstall and reinstall the service since this only adds registry info regarding the executable path and launch options. Just stop the service, copy your assemblies and restart it
You do not need to uninstall the service just make changes in your files after stopping the service and then start again it will consider your changes..
I would suggest you to use Topshelf for service hosting.
来源：https://stackoverflow.com/questions/26253357/do-you-need-to-re-install-a-windows-service-after-rebuilding