As I recall, the LMS-330 uses the Lowrance blue connector (large format) NMEA2000 connector (the connector diameter will be about a half inch or so in diameter, as opposed to the red, which is a bit larger than 1/4" - the lock ring will determine the color I'm talking about.)
I think the GPS unit (hockey puck looking thingie) connects directly to the head unit, rather than going onto a proper NMEA 2000 network. This changed somewhere along the way, but I'm pretty sure the 330 was before that change.
Installation instructions are on page 30 here (I think - check and make sure it matches yours since the model is different):
To shortcut the installation instructions, you'll connect the power leads (power/data connector on the back), and have a cable between head and GPS units (marked GPS on the head unit, I think.) The network port stays empty.
You may also need to power the NMEA 2K bus as well; I seem to remember having to do one other thing to get it working; but that may have been to pass data to the VHF. Sorry, it's been a while.)