What options exist to use a laptop in a boat that's got a Raymarine E-80
setup?

I'd like to be able to do two things. One being pull a live GPS signal for
laptop nav software (Coastal Explorer). The other being upload/download
waypoints and routes to the E-80. I'd prefer to do this with a minimum of
cabling into the laptop. As in, one serial port not several. The laptop
doesn't have serial anyway so I'd be using a keyspan adapter.

What bridges/interfaces should I consider using?

-Bill Kearney