This is a bit off topic - but I am wondering if it is possible to connect
a Nokia N800 to my laptop at the Nav Station, running Coastal Explorer
software - and display the same screen (Coastal Explorer) on the Nokia?

If you run VNC on the PC you can use any number of VNC client programs to
talk to it. Works great for nearly everything but video and very high color
display. Given the widespread availability of VNC I'd have to guess there
is a client for the Nokia.