Besides Andrew's suggestion you could download SeaClear II or OpenCPN
, both free, to your computer and then with a USB to serial adapter, if you don't have a serial port on the computer (unlikely) connect to the chartplotter. It should show your position.
This would take a couple hours to work through, but you would also end up with a backup to the chartplotter in the future.
You would have to get a USB GPS puck
for position if the chartplotter was down and you were using the computer as a chartplotter.
On the baud rate I'd start with 4800 on both if you don't have the manuals