Can I use an external GPS receiver by connecting both GPS and Android device to a PC?
I don't know if you can do this with your PC. Likely the easiest way would be to hack up a custom script on your PC to respond to new positions coming from gpsd, and use the following command to mock those locations on the phone:

adb shell setLatLon latitude longitude

You need to have previously turned on USB debugging and mock locations in the phone's settings.

However, this seems unnecessarily complicated. If you search for external gps on Google Play, you'll see a zillion apps that allow you to connect your Android device directly to an external GPS receiver. There's no need to involve your PC at all. Try a few and report back which one works best for you.