Good Afternoon Cap'
As far as a "plug n play" gps receiver, I use this little jewel.
USGlobalSat-BU353-S4-USB-GPS-Receive Fire up Nx, plug it in to a usb port, and away you go. No need for drivers on the included CD. You can check it is functioning by opening "GPS Panel" (found under Main Menu > Navigation > GPS Panel) or GPS Satellites (Same location) It will take 60 sec or so to acquire an initial fix.
OpenCPN should not care what charts you are using as far as the GPS goes. If you have charts installed that are viewable, your current location should show up once any functional GPS is installed.
Do to the magic of gpsd, you should not have to mess with virtual com ports, serial ports, or much of anything else. (Thank you Nx)